No travel restrictions will be put in place. Milwall have been allocated 1,500 tickets for the game.
Elland Road chief executive Shaun Harvey said: "We felt it was important to keep the game on a Saturday, and with a kick-off time of 3pm, to limit the disruption for our supporters.
"Most people would probably have expected the game to be moved, but we've spoken to Millwall and the police and we want to make this work.
"The vast majority of supporters will cause no problems, but we need the minority to co-operate as well.
"The decision is in the interests of everyone and we need the help of the supporters to make sure the game passes off without any trouble."
Harvey's comments have been supported by Millwall's chief operating officer Andy Ambler.
Ambler said: "It is absolutely imperative that both sets of fans ensure the day passes off without incident so future restrictions on travel or changes to kick-off times are not even considered."