Yes, it can be worn alone. I have the short sleeve one in the same fabric (that is no longer available or I'd order 10 more!) and I wear it alone all the time. My long sleeve one I usually wear under something, but only because I don't think the plainness of they style is as professional looking (and I have my Kates for that purpose). It's not see-thru or anything and the fabric is attractive. It does run large - I have a medium in it like all my Ibex stuff and it's definitely bigger than everything else I have. They may be compensating for shrinkage, but I haven't put mine in the dryer, so I don't know.

I actually have a black LS one in my shopping cart right now, but I'm trying really, really hard not to purchase (that, and a zephyr and a shak for my husband...)!