On April 3, 1927, a fire at St. Andrew's Church forced parishioners to worship at the Methodist Church on Cedar Street while repairs were being made. This fire provided both congregations with the opportunity to get to know each other before the union officially took place in Sudbury. The time spent together also helped to resolve the outstanding issues and on June 10, 1927, Sudbury's Methodist and Presbyterian parishioners joined together as part of the United Church of Canada. With this union, St. Andrew's became one of the largest congregations in Sudbury and the biggest in the Protestant faith.
St. Andrew's grew to become the central United Church in both the Sudbury District and Northern Ontario. The parish is credited with assisting in the expansion of the United Church throughout the Sudbury area.
Upon uniting, it was agreed that the Methodist Church would serve as the Sunday School for the congregation and that St. Andrew's would become the main church for services. Two days after a union was obtained, St. Andrew's Presbyterian Church was reopened and its name changed to St. Andrew's United Church.
The church enjoyed many fruitful years as membership continued to thrive and harmony was attained between the former Methodist and Presbyterian members.