The design of Don Mills was informed by five planning principles, which had not been implemented in Canada before. The first was the neighbourhood principle, which broke down the community into four neighbourhood quadrants, all surrounding a regional shopping centre. Each quadrant was to contain a school, a church, and a park.
The second concept was the separation of pedestrian and vehicle traffic, which was accomplished through the creation of a network of pedestrian paths providing easy access through parks to area schools and the town centre, while roads were designed to slow vehicular traffic through the use of winding roads, T-intersections, and cul-de-sacs.
The third concept was the promotion of Modern architecture and the Modern aesthetic. Don Mills Development controlled the architectural design, colours, and materials of all buildings in Don Mills. As well, the corporation insisted that builders use company-approved architects, who had been educated according to Bauhaus principles, to prevent the project from deteriorating into a typical post-war subdivision of builder's homes.
The fourth concept was the creation of a greenbelt linked to a system of neighbourhood parks that would preserve the beauty of the surrounding ravines.
The final concept was the integration of industry into the community, which followed Howard's ideals for the Garden City. Planners felt that it was important for residents to live and work in the same satellite (new) town so that Don Mills did not become a bedroom community. A sizeable number of high residential densities–-rental townhouses and low-rise apartments-–was essential if the town were to attract a cross-section of residents working in local industries. Today, Don Mills is home to Global Television, Rogers Cable, and IBM Canada.