Career
Árni began his career with ÍA and made his senior debut during the 1973 season. He went on to play 199 league matches for the club, scoring 28 goals. During the winter of 1978-1979, he had a spell with Dutch Eerste Divisie side SBV Excelsior, where he scored twice in four appearances.
In 1987, Árni joined 3.
In total, he played 64 league matches for Stjarnan and scored 42 goals. Árni played three games for Aris Bonnevoie in Luxembourg in the 1990-1991 season, before signing with Dalvík upon his return to Iceland.
After a year with Dalvík, he returned to Stjarnan for one season before retiring from football in 1992. He netted his first senior goal for Iceland in his second match, a 1–1 draw with Norway.
Árni went on to make 50 appearances for his country over the following 10 seasons, scoring four goals.