With Olivier Giroud sidelined by a broken tibia, Yaya Sanogo started up front for Arsenal at promoted Leicester and he played a central role in the visitors' 20th-minute opener.
The French striker could not find a way past Kasper Schmeichel from Santi Cazorla's dinked pass, but Alexis Sanchez followed up to slam home his first league goal since signing from Barcelona.
Arsenal's lead was to last only two minutes, however, as Jeff Schlupp motored down the left wing before delivering an inviting cross that Leonardo Ulloa powered past Wojciech Szczesny with a firm header.
Arsenal centre-back Laurent Koscielny hurt himself in a clash of heads with Schlupp when the score was still 0-0 and he made way for Calum Chambers shortly after Ulloa's goal.
Leicester came closest to scoring a winner, but Ulloa clipped an effort into the side-netting after cutting inside Chambers and Szczesny produced a diving save to thwart substitute Jamie Vardy.
The result left Arsene Wenger's side four points below leaders Chelsea in seventh place in the table, while Leicester moved up to 15th.
