The Gunners have not had it easy in the Europa League knockout stages this term, having lost the first leg in both the last 32 and last 16.
But after falling to BATE Borisov and Rennes respectively, the Gunners turned things around in each of those second legs at the Emirates Stadium to reach the competition's quarter-final stage.
Arsenal beat Napoli 2-0 at in north London on Thursday to overcome their first-leg troubles in Europe.
And Mertesacker, who retired at the end of last season to become the club's academy manager, now believes the Gunners can go all the way, though he cautioned them ahead of a difficult second leg in Naples.
"Definitely," Mertesacker told Goal when asked if Arsenal can go all the way in the Europa League.
"The team is in the midst of the fight for the top four in the league, has the Europa League and has grown throughout these experiences.
"The first leg was great, but in Naples - the city, the fans, the special atmosphere - it can quickly go in the other direction.
"We are glad that we did not concede a goal. Nevertheless, the chances for the semi-final are good - and we have to make up for that after last year's elimination."
Arsenal reached the semi-final of last year's Europa League, but were knocked out by Atletico Madrid in a 2-1 aggregate result.
Atletico would go on to win the competition by defeating Marseille 3-0 in the final.
The Gunners are currently in a top-four battle in the Premier League, holding onto the fourth-place spot on goal difference over Chelsea.