The 45-year-old actress discussed her relationship with the 40-year-old Coldplay singer on Thursday's episode of The Late Show with Stephen Colbert after announcing her engagement to producer Brad Falchuk.
"He's really like my brother," she said of Martin. "We're very familial. It's nice. It's great."
Paltrow and Martin announced their split, or "conscious uncoupling," in March 2014 after 10 years of marriage. Paltrow, who shares 13-year-old daughter Apple and 11-year-old son Moses with Martin, denied she and the singer are "more evolved" than others for remaining friendly after their divorce.
"Definitely not. No, but divorce is terrible. It was really painful," the star said.
"It was really hard, and I think we really genuinely wanted our kids to be as unscathed as possible. And we thought, if we could really maintain the family even though we weren't a couple, that was kind of the goal," she explained.
Paltrow confirmed her engagement to Falchuk this month in the new issue of Goop magazine. She spoke in the cover story about finding love again with the American Horror Story co-creator following her divorce.
"Personally, at midlife, I have tried to accept how complex romantic love can be," the actress said.
"I have decided to give it a go again, not only because I believe I have found the man I was meant to be with, but because I have accepted the soul-stretching, pattern-breaking opportunities that (terrifyingly) are made possible by intimacy," she explained.