Marielle Jan de Beur often catches the 6:27 a.m. train to Grand Central Terminal, waiting on the Westchester platform with a swarm of dark-suited men, and then walks 10 blocks to a Park Avenue office fronted by the fountain where Audrey Hepburn cavorted in “Breakfast at Tiffany’s,” playing a woman scheming to marry a wealthy man.

But when the elevator lets her off at Wells Fargo, she enters another zone, where the gender dynamic that has long underpinned the financial industry is quietly being challenged. Ms. Jan de Beur and some of her colleagues rely on support that growing numbers of women on Wall Street say is enabling them to compete with new intensity: a stay-at-home husband.

In an industry still dominated by men with only a smattering of women in its highest ranks, these bankers make up a small but rapidly expanding group, benefiting from what they call a direct link between their ability to achieve and their husbands’ willingness to handle domestic duties. The number of women in finance with stay-at-home spouses has climbed nearly tenfold since 1980, according to an analysis of census data, and some of the most successful women in the field are among them.

When Ms. Jan de Beur flew to Hong Kong last spring to persuade Asian investors to re-enter the bond market, her husband took their daughter to try on confirmation dresses. Her colleagues Allison Poliniak and Gina Martin Adams share a running commentary on their husbands’ efforts in the kitchen. Nicole