A police spokesman said that one other person, Kharbhushan Singh, managed to swim out to safely.
The three deceased have been identified as Vijay Singh, resident of Sharalu, Sanjay Sharma and his wife Chanda, residents of Tangri in Rajouri district, police said.
The bodies have been shifted to Civil Hospital, Gurdaspur for postmortem, they added.
The four persons got trapped in the car after it fell into the canal while one of them managed to swim to safety, police said.