Established officially in 1937, the Toronto Welfare Council was the earliest incarnation of the Community Social Planning Council of Toronto, with its roots in community service agencies dating even further back to 1918. The Welfare Council provided staff assistance on matters of social planning to the Community Chest, and in 1944, joined the Chest in order to establish a stable funding base. Causing controversy at the time, The Council was responsible for the publication of the famed "Red Book" or The Cost of Living Study, a publication that outlined shortfalls in levels of relief and working wages. This groundbreaking work helped to establish a ‘market basket’ approach to research methodology in the field of income security.

Responding to growing concerns related to housing, single mothers and adoption, The Welfare Council pushed for independence from the Community Chest, and sought to build a new organization under the stewardship of the United Community Fund. On May 7, 1957, at a dinner meeting in the Dinner Hall at Hart House, the Social Planning Council of Metropolitan Toronto was formally established. Florence Philpott was named its first Executive Director.

New social movements of the late 60s pushed the Council to refocus on pressing issues within Toronto, and include more representation of grassroots community groups as well as people living in poverty on the Board of Directors. By 1972 the Council had successfully restructured itself to begin work on a wider social development agenda with community organizations and activists. This broader interpretation of social planning manifested itself effectively throughout the 70's, and the values of social development and empowerment still inform the work of the Council today.

As the provincial government moved to amalgamate Toronto in 1997, the Social Planning Council of Metropolitan Toronto and its local planning organization partners, started discussions about their own transformation for the new Toronto. They merged into a unified structure under the new name of Community Social Planning Council of Toronto, which was officially incorporated on January 1, 1998, the same date as the new City of Toronto itself.

In recent years Social Planning Toronto has renewed its commitment to action-based research and policy analysis, focusing on the social service sector in Toronto, the changing nature of work and income in the city, and the social and economic inclusion of newcomers and racialized commnunities.