Wednesday's win for the Asian champions from South Korea means they claim fifth place in Japan ahead of Sundowns.
Kim Bo-kyung, Lee Jong-ho and an own-goal from Ricardo Nascimento gave Jeonbuk a 3-0 lead before half-time.
Percy Tau scored for Sundowns early in the second half before Kim Shin-wook's header sealed the win.
Sundowns lost to Japanese champions Kashima Antlers 2-0 in their other game on their debut at the tournament on Sunday.
African Champions League winners Mamelodi Sundowns of South Africa lost again at the Club World Cup going down 4-1 to Jeonbuk Motors in Osaka.