On 17 March 2006, the New Zealand Knights announced that Brockie had decided to leave the club and join Sydney FC on a two-year contract. Brockie failed to find a regular place in Terry Butcher's first team, included in the starting line-up just twice and figuring in only seven matches of the A-League season. Despite being named in the Sydney FC squad for the AFC Champions League, Brockie was released early from his contract on 6 March 2007 for personal reasons. In July 2007 Jeremy signed for Hawke's Bay in the NZFC, and later for Team Wellington.
In January 2006, he received his first call-up for the All Whites, the New Zealand national team, for the series against Malaysia in February 2006. On 19 February 2006, Brockie made his international debut, coming on as a substitute and playing the last twenty minutes of New Zealand's 1–0 win over Malaysia at Christchurch's QE II Stadium. On the 2006 All Whites tour of Europe, he also made appearances off the bench against Georgia, Estonia and Brazil. Brockie has also represented New Zealand at Under-23 and Under-20 level.