After the revolutionary years, Fabijan Jaremič settled in Vilna where he served as a chief of a telephone-telegraph station. From the very beginning of his stay in Vilna Jaremič became a leading and influential member of the Belarusian community. He ran for the Polish Sejm and was elected three times. In the Polish Sejm Jaremič served as chairman of the Belarusian Representatives' Club. Jaremič made numerous speeches on the floor of the Sejm and took part in several international conferences, defending the human and civil rights of the Belarusians. He edited the newspaper Sialanskaja Dola. Because of his Belarusian activities and his vocal protests against Polish policies in Belarus, Fabijan Jaremič, although a member of the Polish Sejm, underwent regular, periodic harrassment by the Polish authorities.
During World War II Jaremič participated in Belarusian life and paid for his efforts with ten years of imprisonment by the Soviets. After spending a decade in jails and labor camps, he was permitted to return to Vilna, where he died soon after his return, on June 26, 1958.
References: Źnič, Rome, no. 48, 1958, pp. 4-5; Baćkaŭščyna, Munich, August 3, 1958; Biełaruski Kalandar, Vilna, 1923, p. 34.