Kelly A. Frank was arrested along a highway in northwestern Montana, Lake County Sheriff Lucky Larson said.
Frank, 45, and William J. Willcutt, 22, escaped Friday from a ranch operated by the Montana State Prison.
The search for them moved about 120 miles south Tuesday after a vehicle found abandoned in the woods was traced to an area near the ranch. The car's owner said his house had been burglarized, and three weapons were missing.
Authorities said the men were considered armed and dangerous.