Opening night for an opera performance can be a highly publicized event. Therefore check your ticket stub to determine which night of the performance you will be attending. If it is opening night, it is appropriate to dress for the occasion. Ladies, break out your formal dresses. Men, do not be afraid to put on a tuxedo.
For the most part, dress is not as formal on any night other than opening night. However, you can still wear formal attire. There will still be countless people in attendance in formal dresses and tuxedos. If you're not comfortable in his style, semi-formal attire is also appropriate. Wear an outfit that you would wear to church. Business attire is another common choice. The important thing is to look classy.
Attending the opera can be a special and rare event. Therefore treat it as such. Accessorize your outfit. Carry an elegant evening bag to complement your formal dress. A cashmere shawl will add a nice touch to the outfit as well. The opera is also a good opportunity to break out that expensive jewelry you stash away for special occasions.
While you will likely observe people at the opera wearing everything from formal attire to jeans and a T-shirt, avoid the latter look. The opera is meant to be a special and elegant occasion. Treat it as such. Leave the jeans, T-shirt and tennis shoes at home. This will prevent you from feeling out of place when you are part of an audience where the majority of people are considerably more dressed up.