Nunez, 25, was part of the Honduras squad for last summer's World Cup finals and has five goals in 37 international appearances.
He joined Leeds on a free transfer earlier in the season after being released by Mexican club Cruz Azul. His move to Glanford Park is initially for one month.
"He can play behind the frontmen and out wide too. He gives us options in good positions and we're hopeful that Ramon can come in and perform for us," said Lee Turnbull, the Iron's chief scout who is currently helping caretaker manager Tony Daws with the first-team.
"it's not every day that Scunthorpe United sign somebody who has played in the last World Cup."