What is the customer service number for robert half? Robert Half Customer Service Phone Number. Phone Number of Robert Half is 1.888.744.9202 . Robert Half is an American company which was developed in the year of 1948 by the hard struggle of Robert Half in New York.Where is robert half headquarters? Robert Half International Headquarters HQ Address: Robert Half International Corporate Headquarters, 2884 Sand Hill Road Suite 200 Menlo Park, CA 94025, United States.Who is robert half? Robert Half International, or commonly referred as, Robert Half, is a global human resource consulting firm based in Menlo Park, California founded in 1948. It is a member of the S&P 500, and is credited as being the world's first and largest accounting and finance staffing firm, with over 345 locations worldwide.