McConnell joined the faculty of the School of Industrial and Labor Relations (ILR) in 1946, a year after it opened for classes. He taught classes on social security and human relations in industry. He became the third dean of the school in 1959, a position he held until he left for the president's post at the University of New Hampshire in 1963. While at Cornell, he also served as dean of the Graduate School from 1955 to 1959.
Under his leadership, Cornell's ILR School developed an interest in labor relations in Latin America and helped create a labor relations department at the University of Chile. The school also set up a faculty exchange program with the University of Istanbul to aid in the teaching of personnel administration and industrial relations. Faculty research reflected the school's international focus, with projects examining longshore labor at European port cities, productivity in the Soviet steel industry and the problems of Puerto Rican migration.
Under McConnell's direction, the ILR School also initiated the International Labor Training Program, which was designed to provide scholarships for American trade unionists who sought careers in international labor affairs.