One of the journalists was filming his show on Facebook Live when he was shot.
The footage showed his broadcast interrupted by gunfire and a panicked woman shouting "Shots! Shots! Shots!".
Police said the shooting happened on Tuesday in San Pedro de Macoris, east of the capital Santo Domingo.
The two journalists killed were presenter Luis Manuel Medina and radio producer Leo Martinez.
A woman was also injured and is undergoing surgery, said local authorities.
The arrested men have not been charged and police say they do not know the motive.
