This study investigates antecedents of change-supportive behavior and how these antecedents vary over the course of an organizational transition. Change-supportive behavior is defined as actions employees engage in to actively participate in, facilitate, and contribute to a planned change. Drawing on the theory of planned behavior, (a) the anticipated benefits of the change, (b) the quality of the employment relationship, and (c) the formal involvement in the change are examined as antecedents. Hypotheses are tested in a two-wave panel of 72 employees from a hospital undergoing a strategic reorientation toward continuous improvement. Formal involvement in the change had stable positive effects in each wave, conducted 18 and 42 months after the change was initiated. The effects of both anticipated benefits of the change and the quality of the employment relationship were moderated by time, such that the former became less and the latter more important as the change progressed from an earlier phase of implementation to a later stage of institutionalization. Moderating effects of time correspond with theory regarding discontinuous information processing and gradual shifts in employees' cognitive models of their relationship with the organization. Implications for managing employee behavioral support in different phases of change are discussed. Acknowledgments: We thank Michael DeKay, Mark Fichman, Paul Goodman, Don Moore, Sandra Slaughter, and Laurie Weingart for helpful comments on an earlier version of this article. Seung Hyun Kim helped with data coding. The H. J. Heinz II chair provided support for this research.