Arsenal closed the gap on Premier League leaders Liverpool to two points after an impressive second-half show cracked Nottingham Forest's resistance at the City Ground.
The Gunners struggled to break down Forest's well-organised rearguard but took the lead after 65 minutes when home keeper Matt Turner allowed Gabriel Jesus' low shot to deflect in as it slipped through his legs at the near post.
Arsenal doubled their lead seven minutes later, cashing in ruthlessly on another Forest error after Gonzalo Montiel gifted possession to Martin Odegaard, his pass setting up Jesus to play in Bukayo Saka for a confident finish across Turner.