Gunners boss Unai Emery had opted against including Sead Kolasinac
and Mesut Ozil in his squad after they were involved in an attempted
car-jacking during the week.
He also named new signings Dani Ceballos and Gabriel Martinelli on
the bench, with the pair coming on as the Ligue 1 side overturned
Pierre-Emerick Aubameyang's opener to win the pre-season trophy.
Alexandre Lacazette limped off injured early as Arsenal dominated the
opening half, Aubameyang smartly tucking home Henrikh Mkhitaryan's
cross 10 minutes before half-time.
But after the break, with changes taking place for much of the half,
Lyon battled back and Dembele struck either side of Martinelli having a
debut Emirates Stadium goal ruled out for handball.
Before kick-off the fans observed a period of applause in memory of Jose Antonio Reyes.
The former Arsenal forward died in a car accident on June 1.