"Congratulations @evalongoria," the 42-year-old fashion designer wrote. "The smartest, most beautiful woman I have ever met. I feel honored to call you my friend. Such a wonderful day filled with Love. We love Pepe so much!!!"
Beckham's husband, David, followed in her footsteps by posting a beautiful picture taken at sunset.
"Feel so lucky and privileged to be part of the most perfect wedding anyone could wish for," his sweet message read. "[Two] people that are loving, generous and have amazing hearts deserved a day that was so special."
Jane the Virgin star Jaime Camil also took to the popular app, sharing a selfie with the newlyweds and singer Ricky Martin.
Camil also snapped a pic with Melanie Griffith at the lavish fête, calling her "strong and fearless" in his caption.
Meanwhile, Martin opted for a black-and-white snapshot, which featured the groom and the Beckhams.
"Love is in the air," another one of his posts read.
Longoria's Desperate Housewives co-star, Felicity Huffman, and her husband, William H. Macy, also made the trip across the border to support the couple. As they made their way to the destination wedding, Huffman shared a silly snap of their pup, who appeared devastated not to be coming along.
"The dog is sad we're going to Mexico and he isn't!" she captioned it.
Other stars in attendance included Penelope Cruz, George Lopez, Katy Perry and Prison Break star Amaury Nolasco, according to People.
Longoria and Baston, 47, dated for three years before Baston popped the question during a vacation to Dubai last December. This is the third marriage for Longoria, who was previously married to General Hospital star Tyler Christopher from 2002 to 2004, and NBA star Tony Parker from 2007 to 2010. Baston has three children from a previous marriage.