She captioned the photo with a simple word, birthday, along with an emoji of a slice of cake and a party balloon.
Sofia split from her fiancé Nick Loeb six weeks ago but it appears the actress is already smitten with the Magic Mike star.
The hot new couple were first introduced at the White House Correspondents Dinner in May.
Joe was said to have travelled to New Orleans to visit Sofia over the 4 July holidays while she was filming Don't Mess With Texas
with Reese Witherspoon.
Sofia Vergara and Joe Manganiello at the White House Correspondent's Dinner
Sofia flew back into Los Angeles after filming ended on Thursday and the couple spent her 42nd birthday evening in Nobu Malibu.
Earlier in the day Sofia had shared a snap of her blowing out birthday candles on her Twitter page
"Happy verde to me with these two amazing women that I luv and admire!!
" Sofia wrote next to a photo shared on her Twitter page. "I will miss u!! @reesewitherspoon and Anne Fletcher❤️❤️❤️."
Sofia Vergara shared this snap on Twitter of her birthday celebrations with Reese Witherspoon
In the snapshot, Sofia can be seen about to blow out a candle on a chocolate cake
, watched by her co-star Reese
, 38, and the film's director Anne.
Sofia and Joe were spotted dining together at the Li'l Dizzy's Café on Sunday for and were "very friendly and took pictures with other diners," an eyewitness told Us Weekly
. During the meal, "They held each other and kissed several times
Just recently Joe, 37, admitted that Sofia, 41, was his dream woman
. "You're gonna get me in trouble. I don't want to be like a home-wrecker. This person is engaged," he said of the actress.