The littlest member of Olivia Munn's family made the biggest difference in her battle with breast cancer.

The Newsroom alum opened up about how her 2-year-old son Malcolm, who she shares with John Mulaney, played an important role in her health journey. Re-posting a video of herself and the tiny tot playing by a kiddie pool in the backyard, Olivia wrote in an Instagram Story April 22, "This moment was last summer when I had already had three surgeries and recovery—mentally and physically—was pretty rough."

"The smallest, silliest moments like this lifted me up every single time," she continued. "My Malcolm."

In the original caption of the video, which she initially shared in January, Olivia wrote, "If I knew earlier in my life that this magical boy would be in my future, I wouldn't have worried so much about all the little things."

Olivia was diagnosed with breast cancer last year, leading her to undergo numerous surgeries within 30 days, including a lymph node dissection and a double mastectomy. Not only did Olivia experience severe pain in the aftermath of the procedures, but the challenges of not being able to pick up her son made recovery all the more difficult.

"Malcolm runs up and he said, 'Mama, pick [me] up?' And I said, 'Oh I can't pick you up,'" she recalled of her returned home from the hospital in a recent interview with People. "He just sat on my leg and goes, 'But Mama, pick [me] up!'"

The 43-year-old continued, "That was probably one of the hardest things because all you want to do is pick up your baby."

However, her partner John—who she's been dating since 2021—was there to guide her through the difficult moments of balancing treatment and parenting duties.

"It would've felt like climbing an iceberg without him," Olivia gushed of the comedian. "I don't think he had a moment to himself."

Praising John, 41, for "being an incredibly hands-on father," she added, "And he did it all happily."

Keep reading to see Olivia and John's sweetest moments with Malcolm.

John Mulaney and Olivia Munn celebrated their son Malcolm's second birthday in November 2023.

The parents took Malcolm to the Gem State in June 2023.

Olivia shared this photo of her family of three on Father's Day 2023.

John and Olivia hit the beach with Malcom in March 2023.

The couple rang in theirMalcolm's first birthday in November 2022, with Olivia joking that her mom Kim was getting "impatient" with the cake-cutting.

John celebrated his 40th birthday with Olivia and Malcolm in August 2022.

Olivia snapped a sweet moment between John and their son on stage at Red Rocks Amphitheatre in Colorado in April 2022.

The family of three posed alongside fellow parents Dan Levy and Rachel Specter with their daughter Penny.

Olivia and John celebrated Malcolm turning 4 months old on March 24, 2022.

"Daddy" John cuddled with Malcolm on his 4-month birthdate before heading out to Texas.

The actress shared, "It's been 4 months since the happiest, chillest baby came into my world."

John peered over at his baby boy in this throwback photo from his birth. The comedian wrote in March 2022, "Four months ago I met a 6 lb boy who changed my life forever." 

Olivia captioned this adorable embrace with a teddy bear emoji.

Olivia shared a pic of Malcolm with his grandma a.k.a. the "retired tiger mom." 

Olivia gushed over her baby boy.

Olivia and John introduced Malcolm to friends Henry Golding and Liv Lo Golding, as well as the couple's daughter Lyla, in January 2022. 

John and Henry were seen laughing as they held up their tiny tots.

The friends snapped a selfie while introducing their babies.

As Olivia wrote, "Malcolm met Lyla today."

Olivia and John were pictured arm-in-arm during a sweet moment, seemingly gazing at their little one in January 2022.

"Uncle" Pete Davidson visited Malcolm in January 2022.

John gave his son a kiss on the cheek.

Malcolm fell asleep in dad's carrier during an outing at the Norton Simon Museum in Pasadena, Calif.

The Newsroom actress celebrated New Year's Day 2022 with a new pic of Malcolm.

John shared a selfie with his Malcolm, kept cozy in a blue beanie, while they took a walk.

Olivia shared that this was what it looked like "when your friend shows up and surprises you with a blowout even though you're in your robe and not going anywhere."

She said the new 'do made her "feel a little less post partum."