Mountain Lion is OSX 10.8 not 10.9. Yes it will work, but stay away from Rosetta. It's over-hyped, overpriced, and very disingenuous with what services they offer. I was burned when purchasing Levs 1-5 and expecting unlimited Studio Sessions only to get less than 1 hour a month. So the three month Studio Sessions are a joke, less than 3 hours. Go to your local library and check out Pimsleur.