The 99-year-old church in Sydney's Whitney Pier neighbourhood was slated to close this summer, along with several other Catholic churches in the area.
But parishioners found out Sunday that their lobbying efforts had paid off.
In a letter to parishioners, Bishop Brian Dunn, head of the Diocese of Antigonish, recognized the contribution that St. Mary's has made to Polish culture in Cape Breton.
"In light of the responses and information received, especially that the 100th anniversary of the church will be held in 2013, the pastoral planning committee has recommended that St. Mary's Polish Church remain open for the time being," he stated.
The church is a designated historic site. About 50 parishioners attend mass at St. Mary's regularly.
A delegation of 100 people travelled to Antigonish to plead their case after the closures were announced in January. Many wore traditional Polish clothing. They also presented information about St. Mary's financial situation, arguing the church was able to support itself.
Parishioner Tom Urbaniak told CBC News that six binders were submitted to the diocese, including a multi-year plan for the parish.
The letter from Dunn also states that the diocese cannot sustain the current number of Catholic churches in the Sydney area.
In January, church-goers in the area were told the number of parishes would be slashed from 10 to four. Our Lady of Fatima, St. Theresa's and Holy Redeemer would remain, along with either Sacred Heart, St. Anthony Daniel or St. Joseph's.