I have small ears, and I was wondering if there's any plastic surgery procedure that makes your ears bigger.

There are ways of adding tissue to your ear, but they are usually used for reconstruction after something like cancer surgery.  For purely cosmetic reasons, it would be hard to make them larger and have it look natural.  I advise you not to pursue it.

Your ears can be made larger or reconstructed, but pictures or an exam will be necessary to make a determination.Kenneth Hughes, MDLos Angeles, CA

Yes this can be done. There are many options depending on what you are talking about. You can add cartilage to the ear and also skin. Pictures and a consultation would be the first thing to do.