Terzić was an assistant coach of Slaven Bilić at Beşiktaş J.K. between 2013 and 2015 and at West Ham United from 2015 to 2017.[11] His collaboration with Bilić started in 2012, when Terzić drafted and delivered a pre-game opponent analysis for Croatia's group stage match against Ireland at Euro 2012.[12] Satisfied with the analysis, Bilić offered him to join him as assistant coach at Lokomotiv Moscow, however, the deal eventually fell through.[12] Bilić offered Terzić once again to join him at Beşiktaş, and Terzić accepted the offer after consulting with Borussia Dortmund.[12] He followed him to West Ham United in 2015, but left the club two years later when Bilić was sacked on 6 November 2017.[13]