Does buttercream need to be refrigerated?

depends...please elaborate. What type of buttercream, where is your geographical location and do you have airconditioning.

What kind of buttercream? Generally, since its mostly butter and sugar it's pretty shelf stable. If I'm not going to use it for a couple days, I'll refrigerate it....but unless its really hot out, you're going to be fine leaving it out. I'll often make it one day and leave it out to use the next day. I prefer the texture.