Is It Normal for One Breast to Be Bigger Than the Other, After Having a Breast Lift?

Don't expect your breast to be perfectly symmetrical at any time. However shortly after mastopexy significant asymmetries may exist due to asymmetric swelling. These will improve with time.

Early swelling and asymmetry is certainly possible after a breast lift.  Give it time to settle out.  Re-evaluate at one  year.  

Probably if you looked at your pre op photos, one breast will be bigger than the other - so this is usually normal. Talk to your doctor.