Earlier this year CBS lost a group of affiliate stations which defected to Rupert Murdoch's Fox network, an event that contributed to uncertainty over the future of CBS.
It was known to be talking to Westinghouse, but the timing of yesterday's signing was seen as a boost for CBS in a week when many analysts and investors were questioning its future.
It is still seen as a takeover target, and speculative buying helped to push up its share price yesterday, with rumour suggesting several possible bidders, including Walt Disney.
Yesterday's deal between CBS and Group W, the television station division of Westinghouse, involves a 10-year affiliation agreement with CBS for Group W's leading market stations.
The two companies are also planning a joint venture to acquire more stations, and will merge their advertising sales operations.