The 'Valentine's Day' star has a son, Silas, four, with husband Justin but she is up for expanding their family and thinks it would be "great" if they had more babies.
In an interview with OK! magazine, Jessica said: "Babies are crazy and hectic. But, yeah. I think if it happened to us, it would be great."
The 37-year-old actress joked that she and the 'Mirrors' hitmaker are "working on" having another child, and having fun doing it.
She said: "I mean, we're working on it. We're having a good time. You're making me blush!"
Jessica also opened up about Silas, who is named after Justin's grandfather, revealing the youngster has inherited many of his pop star father's traits.
She said: "Well, he's a very good DJ. I guess you could say he's musician adjacent. He's very funny, which is very much like Justin. It's scary not only does he get the joke but he makes the joke. We're at the part of life, which is very funny."
Jessica also revealed that Silas is an "old man trapped in a little body", despite not yet reaching his fifth birthday.
She said: "I took away his iPad and his life was ruined. He's an old man trapped in a little body. He's been here before, I think."
Jessica first started dating Justin, 38, in January 2007 and they eventually wed in October 2012 and after being with him for 12 years she can still remember the first moment that she him.
She recalled: "We'd been introduced by a friend who said, 'Oh, you guys would love hanging out. You should go to this party that Justin is throwing for a friend of his.' And so I went with some girlfriends and my family and that was where we really started to get to know each other.
"After that, we went to the Golden Globes a few months later and we were excited to see each other again. We were both presenting that year, so we said 'Hi' backstage."