Viacom's programming includes Nickelodeon, MTV, Comedy Central, BET, VH1, CMT, Spike TV, TV Land and more.
A seven-year agreement between the two companies expired June 30, and after a deadline extension, a deal still has yet to be reached.
Viacom says Nickelodeon is the most-watched channel on DirecTV.
A dispute between Chicago's Tribune Company and the satellite dish provider was resolved in early April when stations, including WGN, were at risk due to a contract stalemate.
