Wedding Ceremony
For a semi-formal wedding, wear something that lies between casual and formal.
With a semi-formal dress code, you need to ensure that you do not focus too much on the casual side. Since the dress code still requires you to look a bit formal, you must strive to look sophisticated. Men do not need to wear tuxedos, whereas women do not need to wear ball gowns but keep the casual side controlled.
Female guests can wear dressy skirts that are an appropriate length and tops to a semi-formal Catholic wedding. For male guests, dinner jackets and slacks are a safe option.