Roma have completed the signing of a loan signing for the remainder of the season.
The 27-year-old will link up with the Serie A side on a permanent basis after he has played every minute of the last two seasons for the Giallorossi.
The former Feyenoord, Genoa, Palermo and Udinese man has already made three appearances for the Nerazzurri.
The signing comes as a relief for Roma after Vermaet had been on loan at San Siro and the move would have required a transfer fee to be paid in full.
Vermaelheen made just five Serie A appearances for Milan in the first half of last season, but he is in line to make more this season with the Nerazioni.