Environmental sustainability has become one of the key issues for strategy, marketing, and innovation. In particular, significant attention is being paid by companies, customers, media, and regulators to development and consumption of green products. It is argued that through the efficient use of resources, low carbon impacts, and risks to the environment, green products can be essential to help society toward the environmental sustainability targets. The number of green product introductions is rapidly increasing, as demonstrated by the growing number of companies obtaining eco-labels or third party certifications for their environmentally friendly products. Hundreds of companies representing most of the industries, such as Intel, SC Johnson, Clorox, Wal-Mart, and Hewlett–Packard, have recently introduced new green products, underlining the need to develop products that create both economic and environmental values for the firm and customers. A review of the literature shows that academic research on green product development has grown in interest. However, to date, only a few empirical studies have addressed the challenge of integrating environmental issues into new product development (NPD). Previous empirical works have mainly focused on a set of activities for the green product development process at the project level. After years of paying no or marginal attention to environmental sustainability issues, most of the companies now generally realize that it would require knowledge and competencies to develop green products on a regular basis. These knowledge and competencies can be varied, such as R&D, environmental know-how, clean technology/manufacturing process, building knowledge on measuring environmental performance of products, etc., that may be developed internally or can be integrated through external networks. Adopting a resource-based view of the firm, this article aims at (1) investigating the role of capabilities useful for companies to integrate knowledge and competencies from outside of the firm on green product development in terms of both manufacturing process and product design and (2) understanding whether green product development opens new product, market, and technology opportunities, as well as leads to better financial performance of NPD programs. To this end, a survey was conducted in two Italian manufacturing industries in which environmental issues are becoming increasingly important, namely textiles and upholstered furniture. A questionnaire was sent to 700 firms, and 102 useable questionnaires were returned. Results show that (1) companies engage in developing external integrative capabilities through the creation of collaborative networks with actors along the supply chain, the acquisition of technical know-how, and the creation of external knowledge links with actors outside the supply chain; (2) external knowledge links play a key role in the integration of environmental sustainability issues into the manufacturing process, whereas capabilities such as the acquisition of technical know-how and the creation of collaborative networks prove to be more important for integrating environmental issues into product design; and (3) the integration of environmental sustainability issues into NPD programs in terms of product design leads to the creation of new opportunities for firms, such as opening new markets, technologies, and product arenas, though not necessarily leading to improved financial performance of the NPD programs.