Ulsan held a 3-2 advantage after the first leg of the semi-final tie, but Jeonbuk overcame the odds to score a convincing win away from home and secure their spot in the final.
First half goals to Choi Jin-cheul and Chung Jung-hwan gave Jeonbuk the lead at the break, and they didn't look back with Lim Yoo-hwan and Lee Kwang-hyun netting in the second half.
Lee Chun-soo pulled one back for Ulsan, but it was to no avail as Jeonbuk won 6-4 on aggregate to go through to their first AFC Champions League final.
Needing to score at least twice to overcome the away goals rule, Jeonbuk got off to the best start possible with veteran defender Choi heading home in the 10th minute to make the aggregate score 3-3.
Things got even better for the Korean FA Cup holders when Chung also headed into the Ulsan net, this time from a Choi Chul-soon free kick, for Jeonbuk to take the lead on aggregate.
The visitors extended their lead in the 68th minute after substitute Lim scored with a low drive from the edge of the box, but Lee Chun-soo got one back for Ulsan just two minutes later to make the score 3-1 to Jeonbuk, and 5-4 on aggregate.
Ulsan rallied hard late in the match, but another Jeonbuk replacement Lee Kwang-hyun sealed a memorable win as he scored from a corner in the 82nd minute.
To rub salt into the Ulsan wounds, Park Dong-hyuk was sent-off in the 90th minute for a reckless foul and his second bookable offence.
Jeonbuk will meet either Al Karama of Syria or Kuwait's Al Qadisiya in the two-legged final to be played on November 1 and 8.