An investigation revealed that Harris had made Internet searches about life without children and how to survive prison.
Justin Ross Harris, 36, was given the maximum sentence after lead prosecutor Chuck Boring said 22-month-old Cooper Harris perished in "the most torturous, horrific, unimaginable way possible."
Harris has said that he forgot to drop his son off at daycare on June 18, 2014 and didn't realize he had left the boy strapped into his car seat until after he had driven for a few minutes after leaving work.
Prosecutors had argued that Harris wanted to be free of family responsibilities.
An investigation revealed that Harris had made Internet searches about life without children and how to survive prison, and watched videos of animals dying in cars in the sun.
In an unexpected twist to the case, a police detective said Harris had texted sexually explicit messages to six women, one of them as young as 17, while his son was baking to his death.
A jury three weeks ago found him guilty of charges including malice murder, cruelty to children and sexual exploitation of children -- in reference to the teenage woman he texted.
In addition to the life term for the murder charge, Cobb County Superior Court Judge Mary Staley Clark tacked on 32 years for the other crimes.
"The evidence that was presented at trial and the jury's verdict basically says it all," Boring said. "The evidence showed that this defendant was driven by selfishness and committed an unspeakable act against his own flesh and blood."
Harris, who was wearing an orange prison jumpsuit with his hands and ankles shackled, declined to speak at the sentencing. He frowned throughout the proceeding but did not show any emotion as the sentence was read out.
His attorney, Maddox Kilgore, said he planned to file a motion for a new trial.
Kilgore told The Atlanta Journal-Constitution last month that there had been "breakdowns" throughout the judicial process.
Prosecutors did not seek the death penalty, saying there weren't enough "aggravating factors," such as additional victims, in the unusual case.
Staley Clark said she recalled Harris had told police and his ex-wife that he hoped to be "an advocate so that people would never do this again to their children."
"I would say that, perhaps not in the way that you intended, you have in fact accomplished that goal," she said.