Causal inference refers to the process of drawing a conclusion that a specific treatment (i.e., intervention) was the “cause” of the effect (or outcome) that was observed. A simple example is concluding that taking an aspirin caused your headache to go away. Inference for causal effects in education might include, for instance, aiming to select programs that improve educational outcomes or identifying events in childhood that explain developments in later life. This entry’s examination of causal inference begins by first exploring the principles of randomized experiments, which are the bedrock for drawing causal inferences. The entry then reviews the design of causal studies, three distinct conceptual modes of causal inference, and complications that can arise that may prevent causal inference.