The former X Factor winner posted his first Twitter message since New Year's Eve today, saying: "I want to thank you all from the bottom of my heart for your incredible support."
He continued: "I'm back. I feel better than ever. So excited for 2014."
Matt, who won the seventh series of X Factor, also shared a photograph of himself with Spice Girl Melanie Chisholm, saying she'd visited him the previous night.
"Got to see my bezzy @MelanieCmusic last night!! The girl is a diamond in human form," he wrote. Mel C then shared the image on her own Twitter feed, saying: "Look who is back and better than ever!"
Matt and Mel worked together before he entered rehab, collaborating on the duet 'Loving You' and filming a very steamy video together that set tongues wagging they were more than just friends. They denied that.
Mel recently told Metro that Matt is "the most incredible vocalist" she has ever performed with, adding: "He really is the most talented singer."
Watch Matt and Mel C's romantic video for 'Loving You' below: