The 2. Bundesliga leader was on the brink of securing its place in the top flight after thrashing Dynamo Dresden 4-0 the previous day.
When second-placed Hamburg was held 1-1 by Osnabruck, leaving it seven points off the pace with two games to play, Uwe Neuhaus' side was able to celebrate.
Arminia's most recent spell in the Bundesliga ended with relegation in 2009, later twice suffering demotion to the 3. Liga before bouncing back.