Yes, the passport must be signed. A passport with no signature is not valid, and I'm surprised to hear some commenter's say they didn't have a problem when presenting a minor's unsigned passport. We had to get my son a passport when he was 2 months old (was born in Tokyo. We're US citizens). If the minor cannot sign their own signature, then one parent must sign (their OWN name) followed by their relationship to the child (i.e., write "mother" or "father" after your name). Sounds like your daughter CAN sign her own name, though, so let her do so. Some adults I know don't have signatures that are "very good" either... Customs officials don't care how "good" or "legible" your signature is, just that it's YOURS. Hope this helps.