10 Investing Mistakes Beginners Make (And How to Avoid Them)

Introduction

DALBAR's 2024 research found that the average equity investor earned 5.5% less than the S&P 500 in 2023, a gap that was not caused by bad luck or unavailable information, it was caused mostly by behavior. Separate research by Barber and Odean, published in the Journal of Finance, found that the average individual investor underperforms the market by roughly 1.5% a year, consistently, across long stretches of time.

None of this happens because beginners are careless or unintelligent. It happens because a handful of very human, very understandable behaviors, panic during a downturn, excitement during a rally, a reluctance to diversify away from what feels familiar, quietly erode returns year after year. This guide walks through the ten most common mistakes, why they happen even to people who genuinely want to succeed, and exactly what to do differently.

It is worth sitting with that framing for a moment, because it changes what the solution actually looks like. If underperformance were mostly about lacking information, the fix would be reading more articles and research reports. Since it is mostly about behavior, the fix looks more like building systems and habits that remove the opportunity for emotional decisions in the first place, automation, a written plan, a fixed review schedule, rather than simply accumulating more knowledge and hoping willpower does the rest.

This guide is part of our larger investing for beginners guide, and it pairs well with our guides on what investing actually means and how to build an investment portfolio.

Mistake 1: Trying to Time the Market

Waiting for the “right moment” to invest, after a dip, before a rally, once uncertainty clears, feels responsible, but it consistently costs more than it saves.

• Why it happens: market timing feels like the smart, careful choice, avoiding risk by waiting for better conditions, even though those better conditions are never reliably identifiable in advance.
• How to fix it: invest consistently through dollar-cost averaging, a fixed amount on a regular schedule, regardless of what the market is doing. This removes the emotional burden of picking a perfect entry point that does not reliably exist.

It is worth acknowledging a slightly counterintuitive detail here: statistically, investing a lump sum immediately tends to outperform spreading it out over time roughly two-thirds of the time, simply because markets rise more often than they fall over long periods. Dollar-cost averaging is recommended anyway for most beginners not because it produces better average returns, but because it removes the emotional barrier that keeps many people from investing a lump sum at all, the better strategy is the one an investor will actually follow consistently.

Mistake 2: Concentrating in a Single Stock or Sector

Putting a large share of a portfolio into one company or sector feels exciting, especially when that company or sector has performed well recently, but it dramatically increases risk compared to a diversified alternative.

• Why it happens: a single stock is easier to feel enthusiastic about than an abstract index fund, and recent strong performance creates a false sense of safety.
• How to fix it: hold a diversified core, an index fund or ETF spanning hundreds of companies, and if individual stocks are appealing, limit them to a small, deliberate portion of the total portfolio rather than a dominant position.

A useful gut check: if a single company’s bad news, a disappointing earnings report, a scandal, a lost contract, would meaningfully damage your overall financial picture, that position has likely grown too large relative to the rest of the portfolio. A genuinely diversified portfolio should be able to absorb any single company performing poorly, even performing terribly, without derailing the broader plan.

Mistake 3: Panic Selling During a Downturn

Selling investments after a decline feels protective in the moment, but it locks in the loss and forfeits the recovery that has historically followed nearly every prior downturn.

• Why it happens: loss aversion is a well-documented psychological bias, the discomfort of watching a portfolio shrink often feels stronger than the satisfaction of equivalent gains, pushing people toward selling to stop the pain.
• How to fix it: decide on an asset allocation in advance, based on genuine risk tolerance, and commit to it before a downturn happens, not during one. Reviewing the plan when markets are calm makes it much easier to stick with during a decline.

Historical data offers some genuine comfort here, though it rarely feels comforting in the moment a downturn is actually happening. Every significant bear market over the past century has eventually been followed by a recovery to new highs, sometimes within months, sometimes taking a few years. The investors who came out ahead through these cycles were almost never the ones who correctly predicted the bottom and bought back in at the perfect moment, they were the ones who simply stayed invested through the decline rather than converting a temporary paper loss into a permanent, realized one.

Mistake 4: Chasing Hype and Hot Tips

Buying into a trending stock or asset because of social media buzz or a confident-sounding stranger online, rather than independent research, is one of the most common ways beginners lose money quickly.

• Why it happens: confidence is easy to manufacture and hard to distinguish from actual expertise, especially for someone new to investing who has not yet developed a feel for what real research looks like.
• How to fix it: treat any hot tip as a starting point for independent research, not a reason to buy. If you cannot explain in your own words why a company or asset is a good investment, that is a signal to slow down rather than proceed.

Social media has amplified this specific mistake considerably. A confident post or video can reach millions of viewers within hours, and momentum itself can temporarily push a price higher regardless of the underlying fundamentals, creating a feedback loop where the price movement seems to validate the hype that caused it. That loop eventually breaks, often sharply, once the buying pressure driven by hype fades and the asset's actual fundamentals reassert themselves.

Mistake 5: Ignoring Fees

A 1% annual fee sounds negligible, but compounds into a significant cost over decades, a difference many beginners underestimate because it is not a visible, one-time charge.

• Why it happens: fees are usually expressed as a small annual percentage rather than a dollar amount taken out of an account, which makes the long-term impact easy to overlook.
• How to fix it: compare expense ratios before choosing a fund, low-cost index funds and ETFs commonly charge 0.03% to 0.10%, compared to a 0.44% industry average for actively managed funds, a gap that compounds into tens of thousands of dollars over a long time horizon.

Beyond the fund's own expense ratio, it is worth watching for other, less visible costs too, account maintenance fees, trading commissions on certain platforms, and advisory fees on managed accounts can all quietly stack on top of the fund's baseline cost. None of these individually seem large, a few dollars a month here, a fraction of a percent there, but added together across decades, they represent a meaningful, entirely avoidable drag on long-term returns.

Mistake 6: Investing Without an Emergency Fund First

Putting every available dollar into investments, without a cash cushion for unexpected expenses, forces selling investments at an inconvenient, sometimes losing, moment when a real emergency shows up.

• Why it happens: investing feels more productive and exciting than parking money in a savings account earning a modest interest rate, especially during a strong market.
• How to fix it: build a starter emergency fund of $500 to $1,000 before investing meaningfully, then grow it toward 3 to 6 months of expenses over time, alongside, not instead of, ongoing investing.

This mistake often shows up alongside another closely related one: carrying high-interest debt while investing aggressively at the same time. If a credit card balance is accruing interest at 20% or more, that guaranteed cost typically outweighs whatever a diversified portfolio is expected to earn, making debt payoff the mathematically stronger priority in most cases, right alongside the starter emergency fund, before investing becomes the main focus.

Mistake 7: Home Bias — Ignoring International Markets

The U.S. represents roughly 60% of total global stock market value, meaning a portfolio invested exclusively in U.S. companies misses out on the other 40% of the investable world, a well-documented bias in investor behavior.

• Why it happens: domestic companies feel more familiar and are covered more heavily in financial news, creating a natural but costly bias toward what feels close to home.
• How to fix it: add a total international stock index fund alongside a domestic fund, a common starting allocation is 60% to 70% domestic and 30% to 40% international, achievable through a single additional fund.

Morningstar's 2026 portfolio analysis specifically flagged “ignoring non-US stocks” as a key mistake carried over from 2025, a year when international stocks notably outperformed their U.S. counterparts. This is not a prediction that international markets will always outperform going forward, it is closer to insurance, a diversified investor participates in whichever region performs better in a given year, rather than betting the entire portfolio on the U.S. continuing its historical dominance indefinitely.

Mistake 8: Checking the Portfolio Too Frequently

Constantly monitoring an investment account tends to amplify emotional reactions to short-term, largely meaningless price movements, encouraging impulsive decisions that a longer-term view would avoid.

• Why it happens: modern investment apps make checking a balance easy and immediate, and short-term price swings can feel urgent even when they carry no real long-term significance.
• How to fix it: set a fixed schedule for checking investments, monthly or quarterly is generally sufficient for a long-term, diversified portfolio, and resist the pull to check more often during periods of high volatility specifically.

Ironically, the periods when checking feels most urgent, sharp downturns or rapid rallies, are exactly when frequent checking does the most behavioral damage, fueling either panic selling or impulsive buying near a peak. Turning off non-essential push notifications from a trading app is a small, practical step that removes a lot of the temptation to check compulsively during exactly these high-volatility windows.

Mistake 9: Investing Without a Clear Plan

Investing without a specific goal or timeline in mind makes it difficult to choose an appropriate allocation or to know whether a portfolio adjustment is genuinely warranted or simply a reaction to short-term noise.

• Why it happens: getting started can feel like the hard part, so the underlying plan, what the money is for and when it will be needed, sometimes gets skipped entirely.
• How to fix it: define a specific goal and time horizon for each investment account, retirement, a house down payment, general wealth building, and let that timeline guide the asset allocation, more conservative for near-term goals, more aggressive for distant ones.

Mistake 10: Buying Assets You Don't Understand

Investing in a company, product, or asset without understanding what it actually does or how it generates value is speculation dressed up as investing, and it becomes considerably harder to hold through a downturn when the original reasoning was never solid to begin with.

• Why it happens: momentum and the fear of missing out can feel compelling enough on their own, without requiring genuine understanding of the underlying investment.
• How to fix it: before buying anything, beyond a diversified index fund, be able to explain in a sentence or two what the investment actually is and why you expect it to perform well. If that explanation is not possible, that is a sign to research further or skip it.

This mistake is not limited to complex or exotic assets, it applies just as easily to a well-known company whose products an investor uses daily. Liking a company's product is not the same as understanding its financial health, competitive position, or valuation, plenty of beloved brands have made poor investments, and plenty of unglamorous, less exciting businesses have quietly performed very well. The explanation test applies equally to both.

Key Takeaways

• The average investor underperforms the market by roughly 1.5% a year, a gap driven mostly by behavior rather than lack of information.
• Diversification and dollar-cost averaging address several of the most common mistakes at once, concentration risk and market timing among them.
• Fees compound significantly over decades, a seemingly small percentage difference can cost tens of thousands of dollars over a long time horizon.
• An emergency fund should come before aggressive investing, preventing forced selling at an inconvenient moment.
• A specific plan and time horizon make it far easier to choose an appropriate allocation and stay the course during normal volatility.

Conclusion

Every investor makes mistakes, particularly early on, the goal is not perfection, it is building habits that prevent the most costly, avoidable errors from compounding over time. Diversification, consistency, low fees, and a clear plan address the vast majority of what separates the average investor's underperformance from the market's actual long-term return. None of these fixes require special expertise, just the discipline to apply them consistently.

For the full picture on getting started the right way, read our complete investing for beginners guide, and see our best investment apps of 2026 guide if you have not opened an account yet.