By Meredith Lepore
Updated Mar 21, 2016 @ 7:45 am
TV personality Kourtney Kardashian attends Sean 'Diddy' Combs Exclusive Birthday Celebration Presented By CIROC Vodka on November 22, 2015 in Beverly Hills, California.
Credit: Jeff Kravitz/FilmMagic

Who says grown-ups can't have a fun spring break too? Over the weekend Kourtney Kardashian spent a little time under the warm California sun and shared a moment from her poolside experience.

The eldest Kardashian sister posted a sexy photo of herself in a tiny, string bikini that only showed her bottoms and amazing abs. "Sunday Funday," she captioned the snap.

The mother of three has made a major effort in the last year to get in great shape and often shares gym selfies post-sweat sessions—sometimes with a famous sister in tow. The hard work has clearly paid off!

Kourtney's relaxing time at the pool followed a busy few days. On Saturday she joined her family in celebrating her brother Rob Kardashian's birthday and earlier in the week she went out to lunch with her kids and had a girls' night out with a few famous friends, including Lily Aldridge and Miranda Kerr.