 Mulder was born in Randfontein and grew up in Randfontein and Cape Town.He completed his secondary education at Riebeeck High School in Randfontein, where he was head boy and Victor Ludorum in athletics.The son of former Cabinet minister Connie Mulder, Pieter first worked as a lecturer at the Potchefstroom University for Christian Higher Education, before being promoted to head of the university's communications department.