Officials say Keel was captured by Arizona State Police 40 miles outside of Benson, Arizona.
Police were actively working to find 57-year-old Keel. He is facing a first-degree murder charge.
Authorities told ABC that Keel was considered to be armed and dangerous.
Lynn is accused of killing his wife, Diana Alejandra Keel.
Diana was first reported missing by her daughter on March 7. Her husband told investigators he'd last seen her leaving their Nashville home with some friends on Friday, March 8.
On March 12, deputies found Diana's body in the woods more than 20 miles away from her home.
Lynn was questioned by police that day, but was later released.
Diana's family said her marriage was not working out. Her mother said she had even planned to divorce her husband, but he'd threatened her.
Diana is not the first spouse of Lynn Keel to have died.
Lynn's previous wife, Elizabeth Bess Edwards Keel, died in their home in January 2006.
Elizabeth died from blunt force trauma to the head, but the medical examiner ruled her death accidental.
Elizabeth reportedly fell and hit her head on the corner of the concrete steps in the front of their house.