U.S. Customs and Border Protection officers say 30-year-old Carlos Ulises Martinez was stopped Friday at the Nogales port of entry.
He was taken into custody after a records' check showed an arrest warrant for the slaying of 21-year-old Francisco G. Moreno.
The Santa Cruz County Sheriff's Department confirmed the first-degree murder warrant and took custody of Martinez.
Martinez was linked to the shooting death of Moreno at an apartment complex on Tucson's southwest side on March 3, 2009.
Authorities say Moreno was shot after he got into a confrontation with Martinez, who was believed to have then fled to Mexico.