Mihajlović received the sixth position on the It's enough – Restart electoral list in the 2016 parliamentary election and was elected when the list won sixteen mandates.[5] The election was won by the Serbian Progressive Party and its allies, and Mihajlović serves as a member of the opposition. He is a member of the assembly committee on the economy, regional development, trade, tourism, and energy; a member of the agriculture, forestry, and water management committee; deputy member of the security services control committee; a deputy member of the culture and information committee; a member of Serbia's delegation to the South-East European Cooperation Process Parliamentary Assembly; and a member of the parliamentary friendship groups with Iran and Kazakhstan.[6]
Mihajlović was chosen as the leader of It's Enough – Restart on April 21, 2018, after the resignation of Saša Radulović. He won the contest without opposition; Tatjana Macura, the only other candidate, had previously withdrawn.[7]
He resigned from DJB's parliamentary group in November 2018 and initially intended to serve in a new group with four other former DJB members. Three members of this group subsequently resigned from the assembly, however, leaving the two remaining delegates below the threshold for official recognition.[8][9] Mihajlović later said that the members who had resigned did so to prevent the DJB leadership from launching serious personal attacks against them; he added that he did not begrudge them their decisions.[10]
Mihajlović initially sought to remain as DJB leader after leaving its assembly group, but he was dismissed by a vote of its main board.[11] On 25 March 2019, he joined the Independent MPs Club parliamentary group.[12]