Yavari, who stepped down as coach of Pas last week following a 2-1 defeat against Persepolis, took charge the Tehran-based team for the rest of the season.
Steel Azin sits just one place above the relegation zone in Iran's Professional League.
“We will support Yavari in his position. He is the only person who can help us at the moment,” Steel Azin owner Hossein Hedayati said.