A native of Yakutsk, Izmaylov attended a navigation school in Okhotsk with Dmitry Bocharov, who became his lifelong business companion.
In October 1778, while visiting Unalaska, he made the acquaintance of Captain James Cook who presented him with an octant in exchange for a letter of introduction to the Kamchatka authorities.
Cook also handed over to Izmaylov a recently drawn map of the western coast of North America, which was to be delivered by the Russians to the British Admiralty.
In 1783–1785, Izmaylov and Grigory Shelikhov made their historic voyage from Okhotsk to Kodiak Island, where they founded the first Russian settlement in America.
Having wintered in Unalaska, Izmaylov visited Saint Paul Island, where he discovered the crew of a Russian ship that had been missing since 1791.