Notice the event description to decide if 'overdressed' applies. Casual means less formal clothing is expected. Seeing everyone in jeans, she realized her cocktail dress was overdressed.
Pro Tip 2/3
Emotional Response
Being overdressed might cause embarrassment or discomfort, as it can make you stand out. He felt overdressed and awkward in his tuxedo at the barbecue.
Pro Tip 3/3
Cultural Difference
What's overdressed in one culture may not be in another. Consider local fashion norms. In her lavish gown, she was overdressed for a simple American dinner party.