The 31-year-old said that she was happy for Kim, who is expecting her first child with boyfriend rapper Kanye West, reported TMZ online.
When a friend broke the news to Paris, she said, "So happy for her, they are perfect for each other."
Paris and Kim, 32, had a rivalry for years due to their very similar career paths and lifestyles, but recently made up and were spotted out together at a friend's party and at an event in Miami.
Meanwhile, Kim's brother Rob has also voiced his delight at the news, which broke when Kanye called Kim his "baby mamma" live on stage in Atlantic City.
"It is beautiful. It is a blessing. The New Year, we have got another child coming, so that is great. Kim's never had a baby, so it is going to be a beautiful blessing," Rob said.