France international Laurent Koscielny scored a 52nd-minute strike in a 1-0 victory over Newcastle United at St James’ Park on Sunday.
The win ensured Arsène Wenger’s men finished a point ahead of fifth-placed north London rivals Tottenham Hotspur and secured the final Champions League spot.
And Szczesny admitted the Gunners celebrations were “a bit weird” considering Arsenal’s target at the start of the season was to win the Premier League for the first time since 2004.
“We celebrated a bit like we had won the Championship which was a bit weird considering the ambition at the start of the season,” he told BBC Sport.
“We were confident, we have not conceded a lot of goals and when we got the goal we were confident of getting the result.”
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