The 38-year-old singer opened up in an interview with People about the 31-year-old model's struggle with the condition following daughter Luna's birth in April.
"For me as a husband, it was my job to do the best I could to support her and understand what she was going through and do whatever I could do to help her. I feel like that's the least I could do," Legend told the magazine.
"[As a man] you don't know internally what it feels like. You should read about it and understand what it is and really just be there to help," he advised. "You need to be present and you need to be compassionate. And we're learning and trying to figure it out as we go. At least do that and try to figure it out together."
Teigen went public with her battle with postpartum depression in the April issue of Glamour. Legend said he was proud of his wife for coming forward and showing that the condition is "hard" for everyone, regardless of their success or resources.
"I'm glad she wrote about it," the singer said. "I think it was powerful for her to let a lot of women know they're not alone, and no matter how much money you have or fame, anybody can feel that."
Teigen was diagnosed with postpartum depression in December after dealing with "painful" physical symptoms and "spontaneous crying" for months. Her condition improved after she started taking an antidepressant.
"I'm speaking up now because I want people to know it can happen to anybody and I don't want people who have it to feel embarrassed or to feel alone," she told Glamour. "One thing I do know is that -- for me -- just merely being open about it helps."