Dressed in a cleavage-baring, white maxi dress, paired with a long, peach jacket and beige sandals, the 34-year-old Keeping Up With the Kardashians star and the boy visited a young female recipient of the Make-A-Wish Foundation charity, which aids children with life-threatening illnesses.
Kim posted on her Instagram page a photo of herself with the girl, who is lying on a bed, smiling.
"Mason & I spent the day with this beautiful soul, Anissa!" Kardashian wrote. "Thank you Make-A-Wish for this special day!"
She and Mason, her sister Kourtney Kardashian's eldest child, were also spotted that day entering and exiting a Toys "R" Us.
Kim was spotted pushing a full shopping cart, which contained some mermaid toys. She had last week shared a photo of her daughter North West, 2, and Mason's sister Penelope Disick, 3, dressed in mermaid costumes and hanging out with a mermaid performer by a pool. The family had recently vacationed in St. Barts.
Kim is expecting her and 38-year-old husband Kanye West's second child, a baby boy, who is due in December.