Police say the 17-year-old boy and 15-year-old girl were pulled from the river on Sunday and taken to St. Barnabas Hospital, where they were pronounced dead.
They were identified as David Luccioni and Crystal Reyes, both of the Bronx.
Police say the teens were swimming near a park at East 180th Street and Boston Road when they were overpowered by the current of the 23-mile river, which cuts a southward path through the Bronx.
A parks official says a sign posted near the river clearly states that swimming is prohibited. The teens may have climbed a fence to get into the water.
In a statement today, the New York City Parks Department said "This tragic accident underscores the seriousness of entering the water in areas that are not designated for swimming. New Yorkers must never swim in areas such as the Bronx River which are designated with "No swimming" signs."
Police officers, firefighters and civilians pitched in to help rescue the two teens.