The crash happened Sunday night at around 7:45 on the northbound side of the Merritt Parkway between exits 41 and 42, and involved two cars and a tow truck.
Fire officials say all of the injured were out of their vehicles when firefighters arrived at the scene.
Officials said three people suffered serious injuries and three others suffered non-life-threatening injuries. They were taken to a hospital for treatment.
The northbound side of the parkway was shut down for about an hour. The Westport Fire Department helped clean debris from the accident scene and the last fire department units cleared the scene just before 9 p.m.
The cause of the crash remains under investigation.
