Daniel James Burda, 36, was taken into custody Friday on suspicion of manslaughter, criminally negligent homicide, abuse of a corpse, criminal mistreatment and identity theft in the death of Dennis Day, Oregon State Police said.
Burda was being held in Jackson County Jail, where records show he had been booked on June 26 for violating probation on a previous robbery charge.
It was unclear if he has an attorney.
Neighbors say Burda had lived with Day and his husband in southern Oregon. Police declined to provide more details and couldn't immediately be reached for additional comment.
"We heard arguments between Dan and Dennis, that Dennis no longer wanted him there and then Dennis disappeared," said neighbor Cheri Workman, who characterized it all as "an unusual situation."
Day was born in 1942. After moving to California, he began performing at age 6. When he was 10, he was among the first children hired for "The Mickey Mouse Club." Day was a founding member of the Mickey Mouse Club for two seasons in the 1950s.
In February, members of Day's family spoke with "Dateline," a television news show, and said the investigation into Day's disappearance had been poorly handled.
Day, 76, was first reported missing last July 15 by his husband, Ernie Caswell, who has memory loss. Day and Caswell moved to Oregon in the 1980s and married in Ashland in 2009.
"I can't imagine that he would leave Ernie," Day's niece told a local NBC affiliate. "They've been married a long time. He loves him; he always has loved him."
Workman told local CNN affiliate KOBI that she last saw Day walking out of his home to visit friends and that he'd be back in a few days - but she never saw him again.
"He wouldn't have taken off walking, being 76 years old," she said.
Day's car was later found at the Oregon coast and a missing person report said Day had uncharacteristically left his dog with a friend on the day he disappeared.
In April, police discovered a body at the couple's Phoenix, Oregon, home. Authorities identified the body as that of Day last month, though they were unable to use dental records or DNA due to the condition of the remains.
"We have known or felt in our hearts for a long time that he was the man," Workman said of Burda. "We're glad to know that they've got him."
The Walt Disney Company is the parent company of this station.