The 31-year-old actress - who has four-year-old Suri with husband Tom Cruise - adores spending time with the youngster and admits she helps keep her spirits high when she`s having a bad day.
She said: "It`s been really wonderful and I love being a mom. Suri comes to the set with me- She is amazing and it`s really fun to share making a movie with her. She brings so much to it.
"She is such a light that you instantly feel better. When I`m working, I feel like, `Wow, this is so magical I get to share this with you, and you give me so much.` It`s really fun."
Katie has spent the past few weeks portraying the late Jacqueline Kennedy Onassis for mini-series `The Kennedys`, alongside Greg Kinnear.
The brunette beauty adored working on the show - which will air on the History Channel next year - because it allowed her to portray the "amazing" woman.
She told US TV show `Access Hollywood`: "She was an amazing mother and she was a very strong woman. She did a lot right."
Katie was also delighted with how movie bosses have allowed them to integrate their family life into filming.
She explained: "We`ve had a lot of fun with all of the kids on set. Everyone brings their kids and we do play dates there and paint pottery. There`s always like a million things going on at once and you just do it."