Adam Battensby smuggled the devices into the game against Sunderland at the Stadium of Light on January 4, a court heard.
The 24-year-old, of Bramley, had bought the items on the internet and thought the rules surrounding them had been “relaxed”, Sunderland magistrates were told.
Prosecutor Neil Fodor said: “Police on duty within the grounds saw two males on CCTV discharging two smoke bombs. Mr Battensby was identified as one of them.
“He told officers he has bought the smoke-generating devices online three to four months ago and that he thought it would add to the atmosphere.”
The insurance salesman admitted possessing a firework at a sporting event. He was given a football banning order which prevents him from attending any Leeds or international games for the next three years.
He could be locked up for six months if he breaches the order and has to surrender his passport when England play abroad.