The deal includes an option for Dynamo to make the transfer permanent at the end of the campaign.
Casimir, who has earned 10 caps for Haiti, featured at this summer’s FIFA World Cup.
The 24-year-old joined Auxerre on a free transfer last summer and remains under contract until 2028. He made two appearances for Will Still’s side this season, both from the bench.
Casimir’s departure follows Francisco Sierralta’s move to Polish club Gliwice on Wednesday. His transfer to Dynamo was completed before the Russian window closed on Friday.
Auxerre sit bottom of Ligue 1 after losing their opening three matches without collecting a point.
