In this article we conduct a plausibility probe of the hypothesis that uneven democratization decreases cooperation within primarily cooperative dyads. This hypothesis is derived from a combination of Remmer's theory of democratization and international cooperation with democratic peace theory. The case of cooperation and conflict between two small powers, Zambia and Zimbabwe, from the latter's independence in 1980 to 1993 fits Eckstein's criteria for a useful plausibility probe. In addition to overall, bilateral and regional interactions between the two countries, we examine relations in the political, economic, strategic, and physical environment issue areas. Methodologically, we combine time series analysis of events coded in the COPDAB format and interviews with policy makers. We find that, although net cooperation between the two countries remained positive during the entire 1980–1993 period, it decreased significantly overall and in economic issues after the beginning of the Zambian democratic transition in June 1990. Our data allow us to trace the process involved in this decline in net cooperation, ruling out some alternative explanations but not concurrent Structural Adjustment Programs (SAPs), and showing how even slightly uneven democratization was an important cause because it decreased similarity and trust, while not decreasing transparency, and increased uncertainty and thus nationalist responses. We conclude that this plausibility probe justifies further systematic research on the effects of uneven democratization on cooperative dyads to test our hypothesis on cases with and without SAPs, and suggests the utility of further probes of the effects of different types of uneven change on various types of dyads.