Daniel Bryant Gray, 31, was booked into a Maricopa County jail late Thursday, charged with manslaughter and child abuse, Sgt. Tommy Thompson said.
Police earlier said 3-month-old Jamison Dean Gray died after his father had gone to a northeast Phoenix sports bar where he worked as a kitchen manager at about noon on Wednesday to check on business.
Outside temperatures were about 100 degrees, but interior car temperatures are frequently much higher.
At first, police said the father was distracted and forgot about the boy.
However, Thompson said investigators developed information that Gray was smoking pot with a co-worker and forgot that his son was in the car.
When Gray remembered, he went and got the unresponsive baby and took him to the bar and called 911.
Daniel Gray and the first officer to arrive at the scene tried to revive the child before an ambulance arrived, Thompson said. The boy couldn't be revived.
Earlier Thursday, before the turn of events, police sent their investigation to the Maricopa County Attorney's Office to determine if charges would be filed.