The 20-year-old came off the bench to make a name for himself at Elland Road when he connected on Helder Costa's 81st minute cross.
It was Nketiah's second goal for the club since joining on loan earlier this month.
The Whites are now top of the Championship table after four games.
Eddie Nketiah scores his first goal in the championship many more to come pic.twitter.com/rpqUL5ca4o
— Adan (@Arsenal357) August 21, 2019