Does strategic planning enhance or impede innovation and firm performance? The current literature provides contradictory views. This study extends the resource-advantage theory to examine the conditions in which strategic planning increases or decreases the number of new product development projects and firm performance. The authors test the theoretical model by collecting data from 227 firms. The empirical evidence suggests that more strategic planning and more new product development (NPD) projects lead to better firm performance. Firms with organizational redundancy benefit more from strategic planning than firms with less organizational redundancy. Increasing R&D intensity boosts both the number of NPD projects and firm performance. Strategic planning is more effective in larger firms with higher R&D intensity for increasing the number of NPD projects. The results reported in this study also consist of several findings that challenge the traditional views of strategic planning. The evidence suggests that strategic planning impedes, not enhances, the number of NPD projects. Larger firms benefit less, not more, from strategic planning for improving firm performance. Larger firms do not necessarily create more NPD projects. Increasing organizational redundancy has no effect on the number of NPD projects. These empirical results provide important strategic implications. First, managers should be aware that, in general, formal strategic planning decreases the number of NPD projects for innovation management. Improvised rather than planned activities are more conducive to creating NPD project ideas. Moreover, innovations tend to emerge from improvisational processes, during which the impromptu execution of NPD activities without planning spurs “thinking outside the box,” which enhances the process of creating NPD project ideas. Therefore, more flexible strategic plans that accommodate potential improvisation may be needed in NPD management since innovation-related activities cannot be planned precisely due to the unexpected jolts and contingencies of the NPD process. Second, large firms with high levels of R&D intensity can overcome the negative effect of strategic planning on the number of NPD projects. Specifically, a firm's abundant resources, when allocated and deployed for NPD activities, signal the high priority and importance of the NPD activities and thus motivate employees to acquire, collect, and gather customer and technical knowledge, which leads to creating more NPD projects. Finally, managers must understand that managing strategic planning and generating NPD project ideas are beneficial to the ultimate outcome of firm performance despite the adverse relationship between strategic planning and the number of NPD projects.