Enterprise tech could learn a lot about gender diversity from American Express. Last month, Intel INTC announced a $300 million initiative to diversify its workforce (see “The business case for STEM education“) while Microsoft, Google, and other tech giants have acknowledged a need to support more female talent. Yet for American Express AXP , the issue is old hat. The financial services giant started its first women’s inclusion group 22 years ago, and groups for underrepresented minorities soon followed. The world’s largest card issuer by purchase volume (and No. 11 on Fortune’s list of Most Admired Companies), American Express now boasts 39% women in vice-president positions and above. Women made up 66% of corporate executive hires in 2014, a statistic that chief diversity officer Valerie Grillo attributes to the many years American Express has been thinking about the issue. In fact, in 2008, just when most corporations were feeling the brunt of the financial crisis, American Express pushed its diversity efforts into full throttle. Why? For AmEx execs, better business performance and retaining top female talent have always been part of the same discussion. “Nobody said we have to do this. It’s just smart business,” says Susan Sobbott, president of global corporate payments. The result is a company that sets an example for other industries that are trying to catch up.

Real results

AmEx’s employee affinity networks, which encompass 30% of employees globally, have grown over the years to 16 groups with close to 100 chapters. Groups for women, minorities, veterans, and LGBT workers support AmEx’s larger mission to create community among the staff but also drive real results for the business. Last year, when AmEx looked to target multitasking moms (who control 70% of household spending), senior execs within the women’s network were brought in as consultants on the project. “It is critical to make the connection between diversity networks and business results so that it is not viewed as a program du jour, but a very important part of our growth strategy,” says Ed Gilligan, president of AmEx and executive sponsor of its women’s initiatives.

Sponsored success

A study co-sponsored by AmEx in 2010 discovered that women are less likely than their male peers to find advocates who champion them for promotions and raises. The researchers concluded that this issue is directly linked to the small gains women have made breaking into upper-management positions at Fortune 500 companies. The research inspired executives like Gilligan to take concrete steps to address the issue, and the company instituted a formal sponsorship program as a result. As of 2014, 25% of senior executive women around the globe who participated in the program were promoted, and 45% moved strategically within their respective levels.

A need for flexibility

A majority of employees split their working hours between office and home, or work primarily from home. To ensure they are attuned to office culture, AmEx offers an engagement network for virtual workers that 96% of participants say has allowed them to succeed. Management also says it helps retain top talent. Kerrie Peraino, an SVP of international human resources, worked three days a week for three years after having her second child and received a promotion during that time. “Had that not been offered to me, I would not still be with American Express,” she says. 

This story is from the February 2015 issue of Fortune.