Wales was making just its second overall appearance at the World Cup and first since 1958.
Bale, who played for Major League Soccer’s LAFC this past season, remained stuck on 41 goals for the national team, despite surpassing teammate Chris Gunter (109) for most all-time appearances.
Iran goalkeeper Ali Beiranvand was ruled out of the game after he sustained a concussion in the opener. Hossein Hosseini started in his place.
Iran, which qualified for the last two World Cups, has never advanced to the knockout round.
The Iranian team has been peppered since its arrival in Qatar with questions about unrest back home. The players, who did not sing the country’s national anthem in their opener in an apparent show of solidarity with protestors, linked arms and sang on Friday.