The South African Super Rugby franchise said in a statement that Oliver would stay with them until June 29, before being allowed to leave for France four months before the end of his contract.
Olivier is currently the most-capped South African centre in Super Rugby, having played in 109 matches for the Bulls after making his professional debut for the Pretoria-based side in 2003.
The 29-year-old, capped 37 times by the Springboks, also had a spell in Japan with Ricoh Black Rams in 2012.
Montpellier have also confirmed the signing of South African centre JP du Plessis, who has previously played Super Rugby for the Melbourne Rebels and Stormers.
Other new names for the 2013-14 season include Scotland international Jim Hamilton, Australia lock Sitaleki Timani, ex-Highlanders utility back Anthony Tuitavake and French under-20 winger Lucas Dupont.