Analysts polled by market research firm FactSet StreetAccount expected net loss of about 30,000 subscribers.
Cablevision had about 2.6 million video subscribers as of June 30, down about 5 percent from the 2.8 million a year earlier.
The company, under pressure to stop consumers from "cutting the cord"and shifting to internet video services such as Netflix and Hulu, has said it would offer HBO's standalone streaming service, HBO Now, and Hulu's video streaming service to its broadband customers.
The company, controlled by New York's Dolan family, said adjusted operating cash flow, a closely watched metric for the industry, fell 2.7 percent to $474.3 million in the quarter.
Read MoreViacom earnings match, but revenue was light
Still, cable revenue rose 1.8 percent to $1.48 billion, as the company raised rates.
Average monthly cable revenue per customer rose 3.8 percent to $158.52.
Cablevision said net income attributable to its stockholders fell to $75.6 million, or 27 cents per share, in the second quarter, from $94.2 million, or 35 cents per share, a year earlier.
Net revenue rose to $1.65 billion from $1.63 billion.
Analysts on average had expected the company to earn 25 cents per share on revenue of $1.65 billion, according to Thomson Reuters I/B/E/S.