Elche will face Granada in the Spanish Liga promotion playoff.
Elche set up a promotion play-off final against Granada after beating Real Valladolid in the last four.
Elche lost the first leg 1-0 and their task became even harder when Oscar doubled Valladolid's aggregate lead after 23 minutes.
But the match changed just before half time when Edu Albacar netted twice in two minutes to put the hosts 2-1 up on the night.
Angel Rodriguez then grabbed Elche's third 12 minutes into the second half to put them 3-2 up overall.