Milan Bolden-Morris' outfit features photos of 15 African-Americans who were killed in police-involved shootings.
It was made by Florida-based designer Terrence Torrence who wanted to "put a story out there" through his fashion.
Milan wrote on Instagram: "Yes GOD is using me to convey a message that's bigger than me."
Milan had asked Terrence to design her dress for the Pahokee High School prom after he designed her cousin's wedding dress.
She wanted something bold, and told CNN: "When someone loses a mother, father or child in unnecessary circumstances, it should not be overlooked but addressed."
Terrence says he took on the challenge and wanted to use his fashion to promote a message.
"With all the killings that was going on, it just hit me one day - you should put that into a dress," he said.
"I wanted to paint a picture and put a story out there through my fashion.
"I wanted to show we could spread our message with not just posters and fliers but also with garments."
Milan's Instagram post pulled in more than 14,000 likes, and more than 500 comments.
Prettyclassy23 said: "Your decision to wear such a beautiful dress will speak volumes without you speaking a word."
Tajuana_gist said: "Great message and a great way to bring awareness."
Kandyroyalhair said: "Thanks for being strong enough to carry such a serious and sensitive subject."