The first formal Croatian association in Ottawa, the Croatian Canadian Club, was established in 1957. Besides various cultural and sports activities, the Club also organized the participation of Croatian Catholics in the Slovak Eucharist celebrations led by Reverend Jozef Vavrovic. Over the next decade, the Club facilitated occasional visits by the following Croatian priests serving in Canada and the United States: The Right Reverend Monsignor Stjepan Lackovic, Reverend Serafin Vistica, Reverend Eterovic, Reverend Rudolf Hrascanec, and Reverend Vilim Primorac.
In 1969, reverend Marijan Jurcevic, a Dominican priest from Croatia, enrolled in the doctoral degree program at the Dominican College of Philosophy and Theology in Ottaw. He combined his efforts with those of three young Croatian theology students, Marinko Zadro, Jure Krišto, and Jozo Jelinić, and offered regular Sunday mass for croatians in the Chapel of St. Jean-Baptiste Parish at 90 Empress Avenue. During this period, religious and social life blossomed with a significant influx of new Croatian immigrants.
In 1971, during the visit of His Eminence, Cardinal Franjo Kuharić, Archbishop of Zagreb, The Right Reverend Monsignor Vladimir Stanković, and Reverand Živko Kustić from Zagreb, some 300 Croatian Canadians attended a meeting rquesting the establishment of a Craotian catholic mission in Ottawa. But the community was deemed insufficiently strong for such an undertaking, and was left to its own devices following the return of the Croatian Dominican priests to Croatia.
On November 4, 1973, at a gathering of over sixty croatian Canadians, a proposal by Mr. Petar Ćulumović resulted in the founding of the Croatian Catholic Community (CCC) which looked after the religious needs of Croatian Catholics until the formation of the Croatian Catholic Parish. The CCC trained several Dominican priests to offer Sunday Mass in the Croatian language. For the next four years religious services were offered by Reverend J.M. Tillard, Reverend Denis Dion, Reverend Brian Francis Beeching, and on special occasions by Croatian priests Reverend Josip Đuran, Reverend Ivan Golec, Reverend Ivica Kecerin, Reverend Jurica Jezerinac, The Right Reverend Monsignor Stjepan Šprajc, Reverend Ivan Bradvica, and Reverend Vlatko Poljičak.
In 1975, the community was visited by The Most Reverand Mijo Škvorc, Auxiliary Bishop of Zagreb, and The Right Reverend Monsignor Vladimir Stankovic, Director of pastoral care for the Croatian Diaspora. Once again, the CCC expressed the need to have a Croatian priest. Two years later, His Excellency Joseph A. Plourde, Archbishop of ottaw, accredited Reverend Tadija Pavlovic from the Diocese of Mostar to serve the Community. However, reverend Pavlovic unexpectedly returned to Mostar in 1979. What followed was truly a blessing. A very devoted and passionate priest from St. Jean-Baptiste Convent, Reverend Martin Skinner, for seven years helped the Community experience remarkable growth and paved the way for the establishment of the Croatian Parish. Flunet in the Croatian language and culture after twice visiting Croatia, he was embraced by the Community.
In 1986, a Croatian priest well known for his dynamic managerial abilities, reverend Vinko Delinac, from the Diocese of Đakovo and Srijem, Croatia, arrived to serve the Community. Later that year, His Excellency, Joseph A. Plourde, Archbishop of Ottawa, established the regional Croatian ethnic Parish located on 170 Hinchey Avenue in Ottawa. The community, through generous donations of skills and funding, completed major renovation of the Church, residence and hall. Also, the Archbishop accredited Reverend Delinac to serve as the Parish priest. In 1993, he was succeeded by Reverend Anto Pavlovic, and in 2000 by Reverend Adam Tabak, both from Diocese Đakovo and Srijem (Archdiocese of Đakovo-Osijek).
Over the years, the community provided generous support to various charitable organizations and cultural exchange programs between Canada and Croatia. In 1991, the parish facilitated the largest humanitarian aid project in the history of the community. It collected and sent 29 shipping containers (450 tons) of food and clothing to the war-ravaged Republic of Croatia.
The parish of St. Leopold Mandić continues to be a vibrant religious and cultural centre for Croatian Canadians living in the National Capital Region.