Small- and start-up firms in the high-tech industry usually engage in networking to overcome resource, knowledge, and competence constraints in creative, innovation-based competition. Quite often, however, network relationships fail due to lack of network capability (NC), defined as the ability to manage and gain benefits from external relationships. In the present study, we propose and examine an updated five-dimension NC construct and test its effect on innovativeness and performance. Two independent high-tech samples of small firms and start-ups support measurement properties of the proposed NC construct and suggest that the often-overlooked dimension in NC research of network relationship building is important to include in a complete NC construct. Doing so can help explain organizational innovativeness and effects on the customer, sales, and innovation performance more effectively. As a result, we find support for the proposed NC scale and the importance of network capabilities for small companies and start-ups to remain competitive.