Donald Lee Gilson, 48, proclaimed his innocence in the death of Shane Coffman before he was injected in Oklahoma with a lethal combination of drugs.
"I'm an innocent man but ... I get to go to heaven and I'll see Shane tonight," he said in his final statement. He was pronounced dead at 6:19 p.m.
Gilson's parents, sister, a friend and a pastor witnessed the execution, and about a dozen members of the victim's family watched from behind a one-way glass.
He became the second person to be executed this year in Oklahoma.
In 1998, Gilson was convicted of first-degree murder in Shane's death in 1995. An autopsy showed fractures to the boy's skull, his collarbone, shoulder blades, ribs, legs and spine and a tooth missing from his jaw.
Court records indicate that four other children who lived with Gilson and girlfriend Bertha Jean Coffman in a mobile home in Cleveland County showed abuse, and two of the children were emaciated. One of the children told investigators that Gilson beat the boy with a board and then placed him in a bathtub as punishment for going to the bathroom on a rug.