The hitherto elusive Baghdadi, who on June 29 proclaimed a "caliphate" straddling Syria and Iraq, made his appeal in a sermon delivered yesterday in the militant-held northern Iraqi city of Mosul.
"I am the wali (leader) who presides over you, though I am not the best of you, so if you see that I am right, assist me," he said, wearing a black turban and robe.
"If you see that I am wrong, advise me and put me on the right track, and obey me as long as I obey God in you."
The video is the first ever official appearance by Baghdadi, according to Aymenn al-Tamimi, an expert on Islamist movements, though the jihadist leader may have appeared in a 2008 video under a different name.
"God gave your mujahedeen brothers victory after long years of jihad and patience... So they declared the caliphate and placed the caliph in charge," he said.
"This is a duty on Muslims that has been lost for centuries," he added, sporting a long and slightly greying beard, as he addressed the faithful from the mosque's pulpit.