The Keeping Up with the Kardashians star is set to walk down the aisle with fiancé Kanye West on May 24, but is fretting that her younger sister may upstage her.
Kendall, the 18-year-old half sister of Kim, Kourtney and Khloé, has become one of the hottest names in fashion after a successful run at recent Fashion Week shows.
"Kim can't forget how everyone kept talking about Pippa Middleton after the Duchess of Cambridge got married to Prince William. She doesn't want a similar situation at her wedding," a source revealed to British magazine Now.
"It's Kim's big day and she doesn't want Kendall stealing her thunder. Kim needs to be centre of attention at her wedding."
Kim, 33, has already walked down the aisle twice before, first when she wed music producer Damon Thomas and then to basketball player Kris Humphries, a union that only lasted 72 days.
It's thought Kim will ask her siblings to be part of her bridal party, but the source says Kim is also feeling envious of youngest sister Kylie, 16, and her youth.
"She wishes she was as young and carefree as Kendall and Kylie. Kim says she feels old, fat and ugly. She's a jealous as hell! Kylie's young, pretty and the camera loves her. Kim wishes she was 15 years younger - but those days have gone forever. She's got a real bad case of the blues," added the insider.