Andrew Ross Sorkin
The demand for exchange-traded funds (ETFs) has continued its remarkable climb in 2025, as investors increasingly seek out low-cost, tax-efficient tools to build their portfolios. Yet, financial experts warn that the growing popularity of ETFs has also led to a rise in common mistakes that can quietly undermine returns.
According to Morningstar data, ETFs attracted approximately $540 billion in new inflows during the first half of 2025 — already surpassing the pace of the previous year. The industry has also seen a wave of innovation, with 464 new ETFs launched by June, positioning 2025 to potentially set a new record beyond 2024’s total of over 700.
“The ETF boom has been great for investors overall,” said Jon Ulin, a certified financial planner and managing principal at Ulin & Co. Wealth Management in Boca Raton, Florida. “But the convenience of these products can also make investors too comfortable. The biggest mistakes usually come not from the ETFs themselves, but from how people use them.”
Below are several common ETF pitfalls that experts say investors should understand before committing their money.
Understanding What’s Inside the Fund
A major misconception among new investors is assuming all ETFs are alike, said Jared Gagne, a certified financial planner with Claro Advisors in Boston.
“ETFs may look similar on the surface, but what’s inside can vary dramatically,” he said. Some track broad indexes like the S&P 500, offering wide diversification, while others are sector-based, focusing on specific industries such as technology, energy, or healthcare. There are also thematic ETFs, built around investment trends like artificial intelligence or sustainability, and leveraged ETFs, which use derivatives to amplify both gains and losses.
“If you don’t take the time to look under the hood,” Gagne warned, “you might think you’re buying a diversified fund, when in fact you’ve purchased something highly concentrated and volatile.”
The Risk of Chasing Past Performance
Experts also caution against “chasing performance” — a common mistake where investors buy into funds that have recently performed well, assuming the trend will continue.
“Investors often get excited about the latest hot theme — whether it’s bitcoin, clean energy, or cannabis — and jump in after a strong rally,” Ulin said. “But what goes up fast can come down just as quickly.”
Michael Lofley, a certified financial planner and CPA with HBKS Wealth Advisors in Stuart, Florida, added that investment decisions should be based on one’s personal risk tolerance, goals, and time horizon, not recent returns. “Markets are cyclical,” he said. “Yesterday’s winners can easily become tomorrow’s losers.”
Overtrading Can Hurt Long-Term Returns
One of the major advantages of ETFs is flexibility — investors can buy or sell them throughout the trading day, unlike mutual funds that trade only once daily. However, this same feature can tempt investors into overtrading, according to Gagne.
“The true strength of ETFs lies in their low cost and tax efficiency,” he said. “But when people treat them like short-term trading tools instead of long-term investment vehicles, they often erode their own returns.”
Morningstar’s 2024 study found that investor behavior had a measurable impact on performance. Over the past decade, U.S. investors in open-end funds and ETFs earned an average of 7%, compared with the 8.2% annual total return of the funds themselves. This 1.2% “behavior gap” largely stemmed from poorly timed buying and selling decisions.
Experts emphasize that successful ETF investing isn’t about timing the market or chasing trends — it’s about discipline, diversification, and patience. As Ulin summarized, “ETFs are powerful tools when used wisely. But if investors lose sight of the fundamentals, even the best products can deliver disappointing results.”
