Kevin Roper, 37, was driving a Walmart truck in 2014 when the crash happened, as the 30 Rock star and others were returning from a show.
Morgan was seriously injured and fellow comedian James McNair died.
Roper can avoid prison and a criminal record as part of his plea deal.
To do so, he needs to satisfy conditions including carrying out 300 hours of community service, according to his lawyer David Glassman.
“He is grateful for the opportunity to accept responsibility and move forward in doing what is required to obtain a dismissal of the charges pending against him,” Glassman told AP.
Roper entered the plea to second-degree vehicular homicide and four counts of third-degree aggravated assault at a New Jersey court.
The crash happened on the New Jersey Turnpike when Saturday Night Live star Morgan and his friends were returning from a performance given by Morgan in Delaware.
Morgan was left in a coma for two weeks and suffered a broken leg, broken ribs and head injuries. Three of the other passengers were also injured and died.
The Walmart supermarket chain previously reached an agreement with Morgan and the children of McNair, 62, who grew up with Morgan in New York.
The National Transportation Safety Board carried out an investigation into the incident and concluded Roper had not slept for 28 hours before the crash, a finding disputed by his lawyer.
The safety board report said Roper had not slowed down sufficiently before the crash, despite warning signs of road works taking place on the turnpike.
It said the truck was doing 65mph in a 45mph zone before the crash happened.
But the board also said Morgan and his friend should have been wearing seat belts and their limo should have had adjustable headrests, which could have minimised their injuries.
Once out of hospital, Morgan said he had not found out about McNair’s death until he came out of his coma. He described the fellow comedian as a “loving” and “warm” man.
Morgan made his first public appearance after the accident in June 2015 and made a surprise appearance at the Emmys three months later.