Arsenal almost took the lead on the one hour mark through Eberechi Eze but his low strike from outside the 18-yard-box struck the goalpost.
Arsenal dropped crucial points in the battle for the Premier League title after they were held to a 1-1 draw by Brentford at the Gtech Community Stadium on Thursday night.
The result means Arsenal have progressed in 19 of 21 UEFA knockout ties after winning the first leg at home.
Arsenal’s victory extends their impressive winning streak this season. The Gunners are third on the EPL log with two wins in two games.
The English side beat the Portuguese giants in a penalty shootout after playing 1-1 on aggregate.
Arsenal, who had scored 21 goals in their last five Premier League games, were strangely subdued in attack.
Despite having the upper hand in the early minutes of the match, Chelsea failed to break through Brentford’s defence.
