He was extradited and later sentenced to 720 days in jail for the violation.
The Tarrant County Sheriff's Office said in a statement that Couch was released just days before he will turn 21 years old and will be under strict supervision as he serves his probation. Couch's blood-alcohol level was three times the legal limit on the night of the crash.
The 20-year-old who drew worldwide attention after a psychologist testified on his behalf and said he suffered from something called affluenza was released just after 8.30am local time from a jail in Tarrant County, Texas. He was sentenced to 10 years' probation and ordered not consume drugs or alcohol.
Tarrant County sheriff's spokesman David McClelland said Couch was released today from the county jail near Dallas after serving almost two years for a revoked probation.
Couch will have a 9pm curfew when he is released and will have to wear a Global Positioning System and alcohol monitor.
Couch was 16 when he was speeding in his Ford F-350 pickup truck on Burleson-Retta Road in southern Tarrant County and came upon people trying to assist a stranded motorist.
"Now, almost five years after this horrific event, Ethan does not wish to draw attention to himself and requests privacy so he may focus on successfully completing his community supervision and going forward as a law-abiding citizen", the lawyers' statement said. Four people were killed.
He pleaded guilty in 2013 to four counts of manslaughter and a juvenile court judge sentenced him to 10 years of probation, defying prosecutors who sought a 20-year prison sentence.
The case had disappeared from the national spotlight when Couch was caught on camera in 2015 apparently drinking at a party.
Mothers Against Drunk Drivers issued a statement calling Couch's release "a grave injustice" to the victims of the crash.
Couch was brought back to Tarrant County and his probation was revoked. She was free on bond, charged with helping her son flee to Mexico. Tonya Couch has been out on bond, waiting to go on trial next month for charges related to her trip to Mexico with her son: money laundering and hindering the apprehension of a felon.