Investing Mistakes Among Millionaires Revealed In deVere Group Survey

A recent survey by deVere Group, one of the world’s largest independent financial advisory firms, highlights the most frequent investing mistakes made by millionaires, providing valuable insights into optimizing wealth strategies in today’s dynamic financial landscape.

The findings, while focused on high-net-worth individuals, offer practical lessons for all investors striving to achieve their financial objectives.

The survey gathered responses from over 230 high-net-worth individuals worldwide, each possessing investable assets of more than $1.5 million, shedding light on key pitfalls and opportunities for smarter investing.

Nigel Green, CEO and founder of deVere Group, comments: “Our findings are a powerful reminder that even those with significant wealth can fall victim to behavioral patterns and outdated ideas that undermine their financial goals.

“These mistakes should serve as a cautionary tale—and an opportunity to refine approaches in a market where adaptability and informed decision-making are everything.

“Importantly, these lessons are just as critical for everyday investors as they are for high-net-worth individuals.”

1. Holding onto the ‘Cash is King’ mentality for too long

The number one mistake, identified by 44% of respondents, was maintaining an overreliance on cash. Many participants believed that holding cash excessively or for extended periods would provide security, especially during volatile times.

“While cash has its place in a balanced portfolio, leaning on it for too long can be a major setback,” explains Nigel Green.

“Excessive cash holdings often erode real value over time due to inflation. In addition, cash doesn’t generate returns or allow investors to take advantage of opportunities in equities, real estate, or other growth sectors.

“Instead of sticking with a ‘cash is king’ mindset, investors should recognize that true wealth growth comes from deploying cash wisely across diverse, income-producing assets.”

2. Making emotional decisions

The second most common investing mistake, highlighted by 31% of respondents, was allowing emotions to drive decisions. Fear and greed often lead to impulsive choices, such as panic selling during downturns or chasing fads at market peaks.

The deVere Group CEO emphasizes: “The market rewards those who remain objective and disciplined. Emotional investing rarely leads to sustainable returns.

“A solid financial strategy, guided by expert advice and based on long-term objectives, mitigates emotional pitfalls and ensures investors avoid the classic ‘buy high, sell low’ trap.”

He adds: “This is precisely why professional advice is so invaluable—it provides a critical layer of objectivity and helps keep emotions in check.”

3. Focusing excessively on historical returns

Coming in third, with 21%, was the tendency to rely too heavily on past performance when making investment decisions. Many investors mistakenly equate historical success with future potential, often at the expense of forward-looking opportunities.

Nigel Green notes: “The classic financial disclaimer says it all: ‘Past performance is not an indicator of future results.’ Markets evolve rapidly, and strategies that worked a decade ago—or even last year—may no longer deliver the same outcomes. The most successful investors are those who evaluate the current landscape and anticipate what’s coming next.

“At deVere, we help clients focus on forward-thinking strategies to stay ahead of the curve, particularly as megatrends like AI, clean energy, and digital assets reshape the global economy.”

The remaining 4% was made up of a variety of answers, including lack of diversification, and investing without a plan.

Lessons for every investor

Nigel Green stresses that while the survey was conducted with millionaires, the findings carry valuable lessons for all investors.

“These common mistakes are not unique to the wealthy—they are universal. Whether you’re a millionaire or just starting out on your investment journey, the same principles apply: avoid sitting on too much cash for too long, keep emotions in check, and always look forward rather than backward when making decisions.”

He concludes: “The results of this survey underscore the importance of stepping back and reevaluating ingrained habits.

“Financial success is as much about avoiding mistakes as it is about making smart moves. This is where expert financial planning makes all the difference.

“By addressing these top three mistakes, investors at all levels are positioned to maximize returns, safeguard wealth, and seize the opportunities of tomorrow.”