Born in Karlovac, SR Croatia prior to the breakup of Yugoslavia, Jaković was brought by his parents to Canada at the age of six following the outbreak of Croatian War of Independence in 1991. They settled in Etobicoke, part of metropolitan Toronto. Jaković took up association football in Canada. He was a four-year letterwinner at Scarlett Heights Academy, and was named team MVP as a junior and senior, captaining both indoor and outdoor teams. He played in the Canadian national youth program, and also for two-time Ontario Cup winner Woodbridge Strikers under Bob Graham. He was a member of the team that competed at the 2004 Dallas Cup, played with former UAB teammate Lukasz Kwapisz. At the age of eighteen, Jaković had a trial with OFK Beograd, but was not signed by the team.
On 28 June 2008, soon to be twenty-three-year-old Jaković joined Red Star Belgrade ahead of the 2008–09 season, after successfully completing a tryout with the team. He officially signed with the club on 30 June 2008. Jaković made three league starts at the beginning of the season under head coach Zdeněk Zeman. However, following a coaching change on 6 September 2008, Dejan lost his spot in the team and failed to register a single league appearance following the appointment of new head coach Čedomir Janevski. At the 2008-09 winter break, Red Star began looking at options to move Jakovic. In December 2008 it was reported he would be sent to FK Rad along with Marko Blažić, another player who started under Zeman but had played sparsely since Janevski took over, as part of a deal to bring defender Nemanja Pejčinović to Red Star. However, by February 2009, no trade had been announced by the teams, and Jakovic was still on the list Red Star players that started preparations for second half of the season.
D.C. United
Jaković signed for Major League Soccer side D.C. United on 27 February 2009. Jaković scored his first goal for the club on 26 May 2012 against New England Revolution, the game ended in a 3–2 home victory. Jaković signed a contract extension with D.C. United following the 2012 season.
Jaković returned to the top flight when he signed with MLS expansion club Los Angeles FC in January 2018. Jaokvic would make his LAFC debut against the Seattle Sounders during the 2018 season opener. He re-signed with Los Angeles in January 2019 ahead of the 2019 MLS season. He moved on loan to Las Vegas Lights on 7 June 2019. He was recalled three weeks later on the 28th. Jakovic's option for the 2020 season was declined by Los Angeles, but he signed a new contract with the club in December 2019.
International career
Jaković made his debut for senior Canadian men's soccer team on 30 January 2008 against Martinique. Later in 2008 he earned five caps for the Canada U-23 squad in the 2008 CONCACAF Men's Pre-Olympic Tournament, during which Canada finished third, one place out of qualification. Jaković was also chosen in the 23-man roster for the 2009 CONCACAF Gold Cup; Canada won Group A with 7 points before being knocked out by Honduras in the quarter-finals. Jaković was selected for the 2011 CONCACAF Gold Cup, however sustained a hamstring injury a week prior to the group stage in a friendly at BMO Field against Ecuador the match ended 2–2. David Edgar was selected on 6 June, to replace Jaković in the 23-man squad for the CONCACAF tournament.
