The actor is in England with several other 'Suits' stars to celebrate the big day, and he shared a heartfelt tweet to the bride-to be, expressing his gratitude.
"Going to bed now and thinking a lot about the strange surreal and wonderful day my friend Meghan is going to have tomorrow," Adams tweeted on Friday. " Meghan - wherever you are - we are so grateful to be here to watch you both take this monumental step together. Love deeply and live well. #RoyalWedding."
Adams and his real-life wife, Pretty Little Liars star Troian Bellisario, came out to the U.K. to celebrate Markle's big day, and shared a number of photos from their fun trip.
The couple were joined by fellow Suits stars Rick Hoffman Gina Torres, Sarah Rafferty and Abigail Spencer -- along with a number of other friends -- for a special dinner Friday evening.
The actor shared a photo of the fun gathering at The Barn, a restaurant in East Berkshire, England, which he captioned, "The last supper."
Suits star Gabriel Macht will also be joining the group to celebrate Markle's nuptials, and has been documenting his European trip on social media.
One co-star who won't be at Markle's wedding, however, is veteran actor Wendell Pierce, who plays the father of Markle's character, Rachel Zane.
Pierce tells ET that he "was unable to attend" the royal wedding, however he will be watching from home.
"[I] will be up in the morning with champagne, strawberries and cream, watching," Pierce said, adding that he is "irrationally happy" for his on-screen daughter and Prince Harry.
The 36-year-old actress and the 33-year-old royal will be exchanging vows in a stunning ceremony at St. George's Chapel in Windsor Castle on Saturday. Check out the video below for more on the famous faces fans can expect to see at the star-studded ceremony.
'Suits' Actor Jokes He Got 'Knocked Out' of Meghan Markle’s Wedding by the Spice Girls (Exclusive)