Gavrilović joined the Socialist Party of Serbia in 1995.[2] He appeared in the third position on the party's electoral list for the Pančevo division in the 1997 Serbian parliamentary election and was given a mandate when the list won four seats.[3][4][5] (From 1992 to 2000, Serbia's electoral law stipulated that one-third of parliamentary mandates would be assigned to candidates on successful lists in numerical order, while the remaining two-thirds would be distributed amongst other candidates at the discretion of sponsoring parties or coalitions. Gavrilović was not automatically elected by virtue of his list position, but he was awarded a mandate all the same.)[6] The SPS and its allies won a plurality victory overall, and the party remained the dominant presence in Serbia's coalition government after the election; Gavrilović served as a supporter of the administration. He was not a candidate in the 2000 Serbian parliamentary election, and his term ended in January 2001.
Gavrilović appeared in the eleventh position on the SPS's list for the Pančevo city assembly in the 2008 Serbian local elections.[7] The list did not cross the electoral threshold to win representation in the assembly.[8]
He sought election to the Assembly of Vojvodina in the 2012 provincial election, running in Pančevo's first division, and was narrowly defeated in the second round of voting. He also received the lead position on the party's list for Pančevo in the 2012 local elections and was elected when the list won twelve mandates, finishing in third place overall.[9][10] The local election did not produce a clear winner, and a coalition government was eventually formed by the SPS, the Serbian Progressive Party (Srpska napredna stranka, SNS), and other parties. Gavrilović was chosen as mayor.[11] He served until May 2013, when he resigned, citing health issues.[12]
Gavrilović later appeared in the twenty-eighth position on the SPS's list for Pančevo in the 2016 Serbian local elections.[13] Election from this position was unlikely, and he was not elected when the list won only six seats.[14]