Serena Williams isn't afraid of adding more to her plate. In addition to her 23 Grand Slam titles, she's also chair of Verizon Media Group's board of advisors, the founder of a venture capital firm, and last year, she launched her own direct-to-consumer clothing line.
For years, she has been a Nike-sponsored athlete. So what was the biggest lesson she learned from working so closely with the apparel and footwear giant?
"Don't get in Nike's space because they do it well!" she laughed, in an interview Tuesday with CNBC's Julia Boorstin. "Nike's such an amazing leader in what they do."
Earlier Tuesday, speaking on an Advertising Week panel, she said that she admires Nike for not being afraid to stand up for what's right and wanting to empower people to do that.
Williams' own clothing line, Serena, is sold exclusively on her website. Williams debuted her dresses, jumpsuits, and more at New York Fashion Week in September.
"We do something a little different. We're more in the fashion, off-the-court type, non-athleticwear," she said. "It's really just about being who you are, loving who you are, and loving our product. It's a direct-to-consumer brand because we wanted to cut out the middle man and bring really great fashion."
Williams also formally announced her firm Serena Ventures this summer, although it has been funding startups by young founders since 2014.
"Our mission is to be more inclusive," Williams said. "When you think of Silicon Valley, you think of a lot of investments, you think it's so exclusive, like 'how do I get in that' and 'I can't invest cause I don't know and there's no way in,' but we want to make a way where it has more inclusivity and more impact."
Serena Ventures has already invested in more than 30 companies including Neighborhood Goods, Masterclass, and Coinbase.
"We really want to take a focus and look at female founders and people that really want to make a difference. It's also important for us to look at people across the board and have a really diversified portfolio," she said.
—CNBC's Jodi Gralnick contributed to this report.