There are three main followers in Diablo 3 for the PC, but how many can you have follow you at once?
Well, of the three main followers, you can only have one follow you at a time. If you get a new follower, your other one will return to town and wait for you to recruit them again.
However there are characters that will follow you during certain quests that don’t replace your main follower, so at certain points of the game you can have up to two followers at a time, but only for a limited time.

nop277 November 27, 2012 at 2:20 pm
Actually at one point when finding Kulle’s stuff I had the templar and Leah following me but it also said Kulle was following even though he didn’t really do any combat. I did though run into a guy who was looking for some crucible in a dungeon and he started following me. So at the time I technically had 4 followers of which 3 were actually fighting.