Ivan Sontsov-Zasekin was a representative of the ancient Sontsov-Zasekin family and the son of Andrei Petrovich Bolshoy (Loban). In 1577, he participated in the sortie at Oreshki, and in 1581, he served as a voivode in Dedilovo.

In the spring of 1583, the advanced regiment commanded by Princes Zasekin and Stepan Vasilyevich Kuzmin-Karavaev, along with the Bolshoy regiment led by Princes Ivan Samsonovich Turenin and Dmitry Andreevich Zamytsky, went down the Volga and established a fortress in Kozmodemyansk.

In 1584, Ivan Andreevich Sontsov-Zasekin was in Mikhailov with the guard regiment, and in 1585, he was a voivode in Belyov.

In 1587, after the Crimean princes captured and burned the fortress of the city of Kropivna on June 30, voivodes with regiments were sent beyond Tula to the Malinovye Gates. They arrived there on July 13 and stayed for a week. As the Russian troops approached, the Tatars began to retreat into the steppes, but the Russians caught up and destroyed most of their detachments. On the right hand were Prince Fyodor Andreevich Nogotkov and Prince Ivan Andreevich Sontsov-Zasekin. He submitted a petition to the Tsar regarding Ivan Lvovich Saltykov, the second voivode of the Bolshoy regiment, and Tsar Fyodor Ivanovich ordered his petition to be recorded.

In 1592, Sontsov-Zasekin, while serving as a voivode in Belyov, was involved in the construction of the city. In 1593, he served as a voivode in Ryazhsk, and in 1598 in Oskol.

In 1600, Prince Vasily Grigorievich Shcherbatov was appointed the second voivode in the Bolshoy regiment in Mtsensk. This appointment affected the family honor of Prince Sontsov-Zasekin, and he submitted a petition to the Tsar against Prince Shcherbatov, believing that his position should not be lower. The Tsar instructed the boyars to investigate this matter. The boyars decided to record in the petition of Prince Sontsov-Zasekin that he should serve without a place, and upon completion of his service, receive a court in his "homeland" and an account against Prince Shcherbatov.

In 1601, in the Ukrainian detachment of the advanced regiment in Novosil, Saburov and Prince Sontsov-Zasekin were supposed to serve, but Saburov did not arrive, so with Prince Zasekin were voivodes from Mikhailov: Yefim Varfolomeevich Buturlin and Pyotr Fedorov.

In 1602, Sontsov-Zasekin was appointed voivode in the advanced regiment in place of Prince Pyotr Akhamashukovich Cherkassky, with whom Ivan Fyodorovich Basmanov served. This caused a dispute over ranks, and Prince Sontsov-Zasekin submitted a petition regarding the account against Basmanov and against the boyar Prince Dmitry Ivanovich Khorostinin. The Tsar left Prince Sontsov-Zasekin in Novosil, while Ivan Basmanov was killed in a robbery attack.

In 1609, Prince Ivan Andreevich Sontsov-Zasekin headed the Kholopey Court and reported to the boyars about additional articles to the Judicial Code.

His son Andrei, who died after 1647, was a scribe and a stolyar. In 1626 and 1629, he served as the first voivode in Pereyaslavl-Zalessky, in 1637 as a voivode in Krapivna, and in 1640 and 1642 in Voronezh.