In the area known as "Poteraiha", a wooden church dedicated to the Holy Trinity was founded in 1718 with funds from the nobleman Pyotr Medvedev, featuring an altar in honor of the Holy Apostles Peter and Paul. The church's foundation was blessed by the Siberian Metropolitan Fyodor Leshchinsky. On January 16, 1721, the altar in honor of the apostles Peter and Paul was consecrated in the Trinity Church by Metropolitan Korniliy, the builder of the Irkutsk Ascension Monastery. Irkutsk chronicles mention that a flood occurred on the Angara River that year, with the water rising about one and a half arshins near the Trinity Church. During a procession around the church, the ice on the northern side broke.

On June 24, 1721, the Beijing archimandrite Antoniy Platkovskiy, who arrived in Irkutsk in March, consecrated the main altar of the church in the name of the Holy Life-Giving Trinity. Later, in April 1858, Irkutsk merchant Yakov Stepanovich Maikov, who had served as the church's elder for over twenty years, planted many trees around the church, including pines, spruces, firs, and cedars. This grove protected the church from a fire in 1879.

Construction of the stone Trinity Church in the Siberian Baroque style began in 1754, featuring an original volumetric solution and a decorative facade. Even before the construction was completed, on May 5, 1763, a warm altar in honor of the Nativity of the Mother of God was consecrated. That same year, a tragedy occurred: on July 19, the vault of the under-construction stone Trinity Church collapsed, resulting in the deaths of three people. This accident delayed the completion of the construction. In 1775, the main altar in the name of the Holy Life-Giving Trinity was consecrated, and in 1778, the altar of the Holy Apostles Peter and Paul. In December 1785, a bell weighing 204 poods was raised to the bell tower of the Trinity Church.

From 1845 to 1847, many Irkutsk churches, especially the old ones, underwent repairs. The Trinity Church was no exception, with repairs conducted in 1846. On January 16, 1866, a parish primary school opened at the Trinity Church, located in the house of Irkutsk burgher S.I. Levin, who provided the premises free of charge. The following year, the school moved to the house of Irkutsk merchant Ivan Nikolaevich Khakhilev. During the flood on January 4, 1870, the school was flooded to the ceilings, and classes were temporarily suspended. However, on November 21, 1870, the parish school reopened in a special building measuring 3×4 sazhen. Initially, three boys and ten girls were enrolled.