Ahmadinejad was accompanied by his close aide Esfandiar Rahim Mashai and Foreign Minister Manouchehr Mottaki, IRNA said.
Qatar pressed ahead with the planned summit over the objections of regional heavyweights Egypt and Saudi Arabia as well as the Palestinian leadership of president Mahmud Abbas.
Iran is a staunch supporter of the Islamist Hamas movement, which controls the Gaza Strip, and does not recognise its archfoe Israel.
Ahmadinejad, who has previously predicted that Israel is doomed to be "wiped off the map", on Thursday accused some Arab and Islamic states of complicity in an Israeli "genocide" against Palestinians in Gaza.