Sevilla have won seven of their past eight La Liga matches.
Levante have lost five of their last six away games.
De Colo, who had four shots on target, had two chances to equalise in the second half.
Sevilla had the better of the first half with goals from Cristian Zapata and Jordi Alba.
Alba had an effort saved by Valdés, while Sevilla keeper Lucas Silva made a superb save to deny Valdés’ header from Alba’s cross.
Levanta were level at the break but De Colo struck in the 80th minute to make it 2-2.
De Leon then converted from a penalty after Ivan Rakitic’s low shot was parried by the Levante keeper.