Following his satisfying spell at Daegu, in 2018 Júnior joined former rivals Ulsan Hyundai on a free transfer. He made his debut with the Kim do-hoon-guided side on February 13, 2018, coming in for Yohei Toyoda at the 76th minute of a 3-3 away draw against Melbourne Victory in the first game of AFC Champions League's group stage. His first match in the K League 1 was actually on March 1, when he replaced fellow first timer Oh Se-hun at the 56th minute of a 2-0 away loss against Jeonbuk Hyundai Motors.