(CNN) She's the first African-American woman to lead an NBA team and says she better not be the last. More than a year after being tapped as CEO of the embattled Dallas Mavericks, Cynthia Marshall says she has turned around the organization's culture and has greatly diversified its top ranks.

Marshall was hired by owner Mark Cuban last year to transform the Mavericks after Sports Illustrated exposed a "corrosive workplace culture" at the organization. Months after the article came out, an independent investigation launched by the Mavericks unearthed a number of instances over more than 20 years of sexual harassment and other improper workplace conduct, including inappropriate comments, touching, and forcible kissing.

Marshall was living in Dallas and enjoying retirement after a 36-year career at AT&T when Cuban called her for help.

"I walked in his office and while he greeted me at the door, he just looked broken. I mean, he looked as if he had been crying," she recalls in the latest episode of CNN's Boss Files with Poppy Harlow . "He was disturbed by it all and just said, 'I need you.' Literally the mandate was, 'I need you to come in and transform the culture.'"

Marshall accepted the challenge.

Cuban, who purchased a majority stake in the Mavericks in 2000, did not face accusations of misconduct, but the independent investigation found that he had made "significant errors in judgment." He agreed to donate $10 million to women's advocacy groups "in recognition of the institutional and other failures" the investigation found.

"I walked into a bad culture," says Marshall. "I walked into a place where the women were not valued and treated the way I would like to see them treated. Frankly, I think we had a problem with how we respected and treated people of color. It wasn't a very diverse and inclusive environment when I got there. And so we needed to do some things."

Within weeks, she had implemented a 100-day plan to turn around the team's leadership and create a non-hostile work environment. The first areas she focused on were developing a women's agenda and creating a values-based employment system, she says. She also sought to bring transparency to the workplace by granting an outside counsel full access to the team's business operations.

When Marshall was named CEO, none of the employees on the executive leadership team were women or people of color. She increased the diversity within the leadership team by promoting from within and recruiting from outside of the organization. Today, 50% of the executive leadership team are women and 47% are people of color.

"We also looked at gender parity in terms of pay, but then we looked at everybody's pay," she says. "There was a discrepancy, but I expected bigger discrepancies. So we fixed those really quick."

But the changes have gone beyond diversity. Marshall also needed to address the cultural issues that led to the harassment and inappropriate conduct in the first place. She and her team set up a 24/7 hotline for employees to report any concerns they might have, established an external advisory council of 27 local Dallas business leaders and implemented ongoing ethics, compliance and unconscious bias training sessions.

"I had to send a message that we were serious about what was going on there. That we would model zero tolerance for inappropriate behavior and for false allegations as well," she says.

'I have to do it for the sisterhood'

Marshall has been a trailblazer throughout her life. She grew up in low-income housing in Richmond, California, attended college on a full academic scholarship at University of California, Berkeley, and became her university's first African-American cheerleader.

She is also no stranger to navigating difficult situations. As a young girl, she was a victim of physical abuse and witnessed her father shoot another man in self-defense, she says. She miscarried four times, lost her six-month-old daughter, adopted four children, and survived stage three colon cancer. Her faith, she says, has helped guide her and give her the strength to take on more challenges.

Before she retired from AT&T, the parent company of WarnerMedia which owns CNN, Marshall was senior vice president and chief diversity officer. Between her personal and professional experiences, she recognized that she was "uniquely qualified" to take on the role at the Mavericks.

"I have to do it for the sisterhood. I have to help create a great place to work," she says.

But she admits she did not know much about basketball before she took the role.

"I am a continuous learner and that's what I love about this job. I am learning the business of basketball and I have a lot of people on the team teaching me the business of basketball," she says.

Her peers -- and her boss -- acknowledge that. "She is driven, smart, compassionate and a realist," Cuban wrote in an email to CNN. "But those don't compare to her thirst to learn. She does whatever it takes."

While Marshall continues to run the organization's day-to-day operations, she often reminds Cuban: "You own it, I run it."

"I had to tell him that again yesterday," she adds.

But she recognizes she did not accomplish all of this on her own. "I own the fact that we have turned around the culture and I didn't do it by myself. I brought some folks in with me. We promoted some people. We created a great diverse leadership team."

Marshall hopes her work at the Mavericks will set the standard for inclusion and diversity in sports organizations.