The club made almost £50m for the same period a year ago.
Despite the profits fall, cash reserves rose to £123m from £115m.
Profit from trading players was £23.2m, compared with £46.1m for the same period a year ago.
Robin van Persie was sold to Manchester United, with players including Lukas Podolski, Santi Cazorla and Olivier Giroud joining the squad.
Arsenal's chairman, Peter Hill-Wood, defended the club's strategy.
He said: "Our ability to compete at the top of the game here and in Europe is underpinned by our financial performance which gives the club strength and independence.
"We know that comes through winning trophies but also through the way we do things and that will remain our constant guide."