The German club's sporting director Max Eberl claims contracts between the two clubs have been exchanged and now need to be signed before the 21-year-old's switch
The 21-year-old, who is the younger brother of Eden Hazard, was signed by Chelsea in 2012 and has spent the past two campaigns on loan at Zulte Waregem.
Hazard was named as the best player in the Belgian Pro League last season but is now set for a temporary move to the Bundesliga.
"We were always going to make an attacking signing, no matter what the situation is with Luuk de Jong and Peniel Mlapa, and this is supposed to be Thorgan Hazard,” Monchengladbach’s sporting director Max Eberl told Rheinischen Post.
"We have exchanged contracts with Chelsea and we have agreed with Thorgan, we have all agreed and now just need to sign the contracts."