Aside from all the drinking and smoking that goes down (it was Hollywood in the 20s, after all), The Artist is pretty wholesome. There are only a few instances of profanity (the middle finger is used for two seconds, and "Damn" appears on an intertitle), zero nudity, and basically no violence. (Zorro antics don't count.)
There's also a surprising lack of sex, given that The Artist is at least a little bit of a romance. (We really wanted Peppy and George to at least lock lips.)
The moment that probably earned this film its rating is George's suicide attempt, which may be upsetting to some viewers.