62-year-old Gerard Dube entered his plea in November at Superior Court in New London and returned for sentencing on Tuesday.
Prosecutors said Dube was driving a tractor-trailer when he rear-ended multiple vehicles slowing for congestion on Interstate 95 in Waterford in October 2014.
The crash killed 26-year-old Darin Robinson, 3-year-old Dacari and 9-year-old Sanaa. Baughnita Leary, Robinson’s fiancée, was driving the car the victims were in.
She sustained serious injuries.