In an interview with Barbara Walters for a People magazine TV special the 30-year-old actress said motherhood so far has proved to be "very magical".
"It's wonderful, and exhausting," Johansson said. "The love is just unbelievable. It's very overwhelming."
Johansson told Walters that so far she doesn't have a nanny instead she admitted to doing "the whole bit" herself.
"I'm nursing, and I love it, I love it. It's the best way to get back in shape."
The Avengers star and husband Romain Dauriac, whom she secretly wed in October, welcomed in their daughter in early September.
Unlike her high profile marriage, and divorce, to hunky actor Ryan Reynolds four years ago Johansson told Walters she likes to maintain a "pretty low-key lifestyle", opting to keep her marriage out of the spotlight.
"I think being in a committed relationship takes work... It's challenging, but when it works, it's really worth it," Johansson said.