Nothing is known of his early life. He was named "megas domestikos" (commander-in-chief) of the Empire of Nicaea, but sources differ on when and by whom: Nikephoros Gregoras records that this was done by Theodore I Laskaris (ruled 1204–1222), but George Akropolites asserts this was done by Theodore I's successor, John III Doukas Vatatzes (r. 1222–1254) soon after his accession. Modern historians generally consider the latter more probable. In 1224 Andronikos was sent to the region of the Scamander river, just recovered from the Latin Empire, in order to organize its administration as "exisotes". This was probably before he was made "megas domestikos". In 1233, he was sent as head of the expedition against the semi-independent ruler of Rhodes, the "Caesar" Leo Gabalas, whom he forced to acknowledge Nicaean suzerainty.