Chasing a comeback after the break, Al-Nassr made a change: Abdullah Al-Khaibari on for Cristiano Ronaldo.
Iñigo Martínez came within inches of pulling one back in the 53rd minute, only to see his shot strike the post. Al-Ettifaq's goalkeeper then repelled an effort from João Félix.
Félix turned provider in the 74th minute, threading a ball through to Sadio Mané. The Senegalese striker burst into the box and drilled a right-footed finish into the far corner, hauling Al-Nassr back into the contest.
The equaliser followed soon after. Félix swung in a corner in the 77th minute and Abdulelah Al-Amri met it from close range, burying his header to make it 2-2.
Al-Nassr kept the pressure on. Al-Ettifaq's goalkeeper saved from Mané in the 82nd minute, and Al-Alami was flagged offside twice in the 89th and 90th minutes.
Then came the winner. Sami Al-Najei drove a rapid counter-attack in the 90th minute and slipped the ball to Mané, who fired home the third from the middle of the box.
The result took Al-Nassr to nine points and, temporarily, to the top of the table. Al-Ettifaq stayed stuck on six, down in sixth place.