A little bi formal wear...
Be casual. Jeans and a button up is what in my opinion is preferred.
Casual. Jeans are ok but neat and clean presentation of yourself is best
Jeans and a nice shirt is fine Costco prefers staff to dress casually and comfortably. just avoid ripped jeans. I was told to wear jeans and a t shirt to work.
It's a very casual atmosphere. A nice polo and khakis will do. Often times the management was wearing jeans and a nice collared shirt.
You should wear something nice but not to formal. for girls maybe like a casual dress. for boys casual jeans.