Sergius (in the world Dmitry Nikolaevich Voskresensky) was born on October 26, 1897, in Moscow to a priest's family. From childhood, he served in the church and received his education at the Moscow Spiritual School and Seminary. He then entered the Moscow Spiritual Academy but could not finish due to its closure. In 1918 and 1922, he worked in civil positions. In 1920, he enrolled in the historical and philosophical faculty of Moscow University but was expelled and arrested in 1923 for anti-Soviet activities. In the early 1920s, he became an ipodiacon of Archbishop Feodor (Pozdeevsky). In 1925, he took monastic vows with the name Sergius at the Holy Danilov Monastery and was soon ordained as a hierodeacon and then as a hieromonk. Due to his administrative abilities, he often defended the rights of the monastery in various institutions. In 1930, he became the rector of the cathedral in Orekhovo-Zuevo and assistant to the deputy Locum Tenens of the Patriarchal Throne, Metropolitan Sergius (Stragorodsky).

From 1931, he edited the "Journal of the Moscow Patriarchate." In 1932-1933, he was the rector of the Resurrection Church in Sokolniki, and on October 29, 1933, he became the Bishop of Kolomna. From 1934 to 1936, he served as the Bishop of Bronnitsy, and from 1936, as the Bishop of Dmitrov. In 1937, he was elevated to the rank of Archbishop and became the manager of the affairs of the Moscow Patriarchate. At the end of 1940, after the annexation of the Baltic States to the USSR, he was sent there to resolve church issues. After the death of Metropolitan Eleutherius in 1941, he became the Metropolitan of Lithuania and Exarch of the Baltic.

During World War II, during the German occupation, Sergius remained in Riga. Initially under house arrest, he soon gained freedom of movement. He took an anti-communist stance and opposed the church schism, convincing the occupying authorities to maintain the exarchate in canonical connection with the Moscow Patriarchate. In July 1941, at his initiative, the Internal Orthodox Mission was established in Latvia and Lithuania, and in August, the Pskov Orthodox Mission. These missions worked on restoring churches and providing spiritual care to the population in the occupied territories.

On April 28, 1944, Sergius was killed on the way from Vilnius to Riga. According to one version, he was killed by SD agents due to his refusal to recognize the election of the Moscow Patriarch as non-canonical and his anti-German statements. According to another version, the killers were disguised partisans.

In the memoirs of A. Gerich, the farewell to the Bishop and his burial at the Riga Pokrov Cemetery is described. The Bishop was brought to the church in the evening, and his coffin was carried into the temple, where a panikhida was served. The funeral took place on May 4, and the church was filled with people who came to say goodbye. The procession was accompanied by soldiers, and the Bishop was buried next to Archbishop John of Latvia (Pommer), who also suffered for his faith.