The landslide was triggered by heavy rainfall and the car was swept away by the debris and fell into a deep gorge, said Sub-Divisional Magistrate (SDM) Yogendra Singh.
The deceased were identified as Colonel Sudip Kumar, 45, of the Garwal Scouts and his wife Sheetal, 40, while the couple's eight-year-old son and driver were injured in the accident and were rushed to Army hospital.
Colonel Kumar was posted at Lansdowne and was going to Badrinath with his family when the accident took place.
The district authorities have issued an adviosry to people to avoid the highway between Badrinath and Joshimath.