The Senior Deputy Commissioner is second in command after the Commissioner. The Senior Deputy Commissioner directly supervises the Department's five civilian divisions; Human Resources Management, Budget & Finance, Information Technology, Internal Audit, and Population Planning. Inclusive within these divisions are also the areas of Capital Planning, Purchasing & Procurement, and Labor Relations.

John J. Antonelli was appointed Senior Deputy Commissioner on June 16, 2003. Commissioner Antonelli first joined the Department in 1978 as a grant manager. In 1980 he was promoted Deputy Director, Fiscal Control Division and in 1986, named Director of the Division.

In 1993, Commissioner Antonelli was appointed Director of Finance for the Department of Homeless Services, where he established the Finance Division of the then newly created City agency, responsible for a budget of $300 million and implementing the agency's accounts payable, banking, and cost allocation functions.

In 1995 he returned to the Correction Department as Assistant Commissioner, Financial Management and Budget, serving in that capacity for three years prior to being named Deputy Commissioner of Administration in 1998. In that position he served as the chief fiscal officer of the Department, administrating a budget of $1 billion annually. Additionally, he also served as the agency's Y2K coordinator, implementing a successful Y2K transition, as well as overseeing the implementation of voice/video teleconferencing between Rikers Island facilities, the Probation Department and parts of the court system.

Commissioner Antonelli holds a B.A. in Economics from York College, City University of New York.