Negotiated Shipbuilding Contracting Act -Extends from June 30, 1976, to June 30, 1979, the authority of the Secretary of Commerce to award subsidies for the construction of vessels with respect to which the price has been established by negotiation between the prospective purchaser and the shipyard. Provides that the construction differential approved and paid by the Secretary shall not exceed 50 percent of the cost of constructing, reconstructing, or reconditioning the vessel, and that if such differential exceeds such percentage the Secretary may negotiate with any bidder and contract with such bidder for such work on the vessel in a domestic shipyard at a cost which will reduce the construction differential to such percentage or less.

Amends the Merchant Marine Act, 1936, to extend until June 30, 1979, (presently exists until June 30, 1976) the authority of the Secretary of Commerce to accept bids for ship construction. Eliminates the requirement that such approval be based upon the existence of a construction-differential subsidy.