In 1912, Father H. Montanar, of the Foreign Missions Society of Paris and former missionary to China, passed through Quebec. Archbishop Bruchési asked him to establish a "Chinese mission" in Montreal. He laid its foundations with Canon G.M. Le Pailleur. The mission expanded and in 1913, Delia Tétreault accepted to take part in this project that she felt to be closely related to the goal of the Congregation. On November 23rd , some Sisters started teaching Sunday school intended for Chinese immigrants. They also visited the Chinese at home, in laundries and hospitals.

In 1916, a small school for Chinese children opened its doors on Anderson Street. Two missionaries from China were called back to take charge of the classes as well as a virgin catechist for religious education. This first school later moved to St. Urbain and Lagauchetière Streets before being closed by the School Board in 1931.

In 1918, an influenza epidemic left many Chinese helpless. Delia took the necessary steps and obtained permission to open a small emergency hospital at 66 Clark Street to take care of the sick. Thanks to the constant presence of the M.I.C. nurses and of several lay volunteers, the clinic lasted till the end of the epidemic in 1919.
The following year, the Chinese Association of Montreal solicited the Missionary Sisters of the Immaculate Conception to take charge of a real hospital for their sick and elderly people.

For the Chinese immigrants of Quebec in 1919, and those of Trois-Rivières, in 1926, Delia and her Sisters organized different services : adult education, youth spare-time activities, visits to families and the sick, help to newcomers, religious instruction for those who wanted it.

In May 1921, four M.I.C. left for Vancouver in order to set up an organization responding to the needs of the Chinese. They started off with classes for children, music lessons as a breadwinner, visits to a refuge for abandoned elderly Orientals. Then, they reduced their own living quarters so as to take in four beggars and inaugurated a small free clinic for street people. In 1927, the Sisters opened a modest hospital and, in 1932, they took care of Chinese, Japanese, Indian and other tuberculous patients. This was the beginning of Mount Saint Joseph Hospital which eventually became a modern general hospital.