Dan Goldie’s professional tennis career lasted only 5 1/2 years. In that time he won four titles (two in singles and two in doubles), peaked at 27th on the singles ranking, and earned a total of $683,000—or less than one one-thousandth of the money he manages today through his Palo Alto financial services firm.
Even half a decade as a pro was far more than Goldie had envisioned. Growing up in the 1970s in McLean, Va., he had one purpose for tennis: as an escape from a domestic life marked by economic insecurity and fear. “My father was an abusive alcoholic,” he says. “I never wanted to go home.” For Goldie, now 51, that instability shaped not only an athletic career, but also a vocation as a financial pro that has earned him more acclaim than he ever found on the hard court.
Goldie’s primary goal was a tennis scholarship; Stanford’s elite program topped his childhood wish list, and Goldie trained without ceasing to get there. By age 15, he was the top 18-and-under player in the mid-Atlantic region.
He could have joined his equally talented peers at Florida’s Bollettieri academy, a tennis hothouse that produced many of the top-ranked contemporaries Goldie later faced (and lost to) on the pro tour—including Andre Agassi, Boris Becker, and Jim Courier. But Goldie’s mother was divorcing his father (who died in 1995), and her income as a bookkeeper couldn’t stretch to cover the steep tuition. Goldie stayed home and absorbed a different lesson. “We went from an upper-middle-class family living comfortably to my mother and me living alone, paycheck to paycheck,” Goldie recalls. “It caused me to place a high value on financial security.”
The fees at Stanford were even steeper, of course. But Goldie’s tennis—a serve-and-volley style that suited his 6-foot-2, 175-pound frame—netted him a free ride, and victories followed. As a junior, he took Pac-10 singles and doubles championships and a national singles crown. In 1986 he was named an All-American for a third time and won NCAA singles and team titles.
With that success as a springboard, Goldie immediately turned pro—and regretted the move almost as quickly. Though he could hold his own against top players—at Wimbledon in 1989 he beat Jimmy Connors in a second-round match—Goldie could just as easily lose to lesser lights. At times it seemed that battling his way to the pros had exhausted his inner drive. “I don’t think I really loved the game the way the top players did,” he says. “I made a mistake, personally, of being too focused on the earnings dimension.”
But Goldie’s fixation on money took him in fruitful directions. He completed an MBA at the University of California at Berkeley while still on the tennis tour. And he traded on his stature as a pro to network with top financial professionals, “trying to get a feel for what this industry is like.”
By 1991, when bad shins made continuing on the pro tour untenable, Goldie was ready to become an insider. Three months after retiring with a 122–117 record, he launched his financial advisory firm. He began with no clients and a minimum buy-in of $50,000. Today his firm manages $700 million in assets for about 250 clients—and the buy-in is $1 million.
At the helm of what’s now one of the larger independent practices in California, Goldie, a registered investment adviser, helps clients with retirement planning, college savings, insurance, and, of course, investing. In the last of these, he’s closely aligned with Dimensional Fund Advisors. A firm based in Austin, DFA offers a family of mutual funds that rely on quantitative models to spread investors’ money across a wide range of assets. Goldie has used DFA funds since early in his career. Their approach is proudly math-wonky—but David Booth, chairman and co-CEO of DFA, tells Fortune that Goldie has mastered it, proving that he can “communicate the often complex ideas of academic finance in simple and intuitive ways.”
A knack for simplicity also shaped the how-to manual for which Goldie is perhaps best known. The Investment Answer: Learn to Manage Your Money & Protect Your Financial Future was a labor of love Goldie co-wrote with longtime client and friend Gordon Murray—a veteran bond salesman who died of cancer at age 60 in 2011, two months before the work reached bookstores.
The book’s central theme is the folly of trying to beat the market. But after Murray’s death, that theme became secondary to the story of a Wall Street insider who found religion about keeping investments simple and honest—thanks to a former tennis ace.
Those narratives helped the book spend a few months on the New York Times advice bestseller list. Goldie says the book’s ideal reader “isn’t interested in numbers or money, but really needs to know this information.” Athletes often fit this description: “They’ve got all these people wanting stuff from them and telling them what to do—that’s why there are so many bankrupt former athletes,” adds Goldie, whose clients include former touring pros.
This fall Goldie will play competitive tennis for just the second time since his retirement, at a Stanford charity event. His game may be rusty, but he doesn’t regret retiring when he did. “I get a lot of psychic value from helping people,” he says. “It is the primary reason I do what I do.”
This story is from the May 1, 2015 issue of Fortune magazine.