Next Generation American Manufacturing Act of 2015

Amends the Internal Revenue Code to allow a tax credit for the purchase (during a specified period of between 5 and 10 years based on the incentive needed with respect to each product) of new products certified as assembled in the United States and consisting of at least 60% of components assembled or otherwise arising in the United States.

Establishes the 21st Century American Manufacturing Commission to conduct research to designate products eligible for such tax credit.

Allows certain start-up companies that are headquartered in the United States a tax credit for up to 25% of their costs for the construction of a manufacturing facility and for the purchase of specialized equipment for use at such facility. Defines a "start-up company" as any corporation or partnership that: (1) first has both gross receipts and qualified research expenses in a taxable year beginning after December 31, 2012; or (2) has both gross receipts and qualified research expenses in fewer than three taxable years beginning after December 31, 2012, and before January 1, 2018.