Researchers have long studied corporate performance metrics for organizational and financial performance. However, we still know little about how to design sustainability metrics that can move organizations towards better societal outcomes. Questions remain regarding the substantive areas of sustainability performance that should be measured, how data should be aggregated, and how metrics can be engineered to reduce greenwashing. In this paper, we propose a framework to assess corporate sustainability metrics based on the level of uncertainty associated with the effectiveness of the metric and its measurement. We consider whether the metric is measuring management processes or outcomes and discuss how the choice of metrics with lower uncertainty may hamper some types of greenwashing. We argue that organizations should use outcome metrics when uncertainty in measuring the performance outcome is low, and process-based metrics when the outcome is difficult to measure or the link between process and outcome is undetermined. When both types of uncertainty are high, it is unclear whether metrics should be used at all. We illustrate our framework with examples of corporate disclosure in the areas of social and environmental metrics. Our framework enriches our understanding of the uncertainty associated with corporate sustainability disclosures and can be useful for government agencies thinking about mandated disclosures, for managers thinking about what metrics to disclose, and for researchers developing or using sustainability metrics.