The most popular method for investigating the mediation of the similarity-attraction link by trust involved first the manipulation of attitude similarity between the partner and the participant and then assessments of trust before attraction. Such correlational data precluded unambiguous inferences of causal flow of attitude similarity effects from trust to attraction. In the present study, we experimentally manipulated attitude similarity first and trust in the partner next, and measured trust in, and attraction toward, the partner after each manipulation. We found that similarity’s impact on trust remained stable over time but that on attraction declined substantially from the first to second assessment. Mediation analyses and structural equation modeling were consistent with a model in which causality flowed from attitude similarity to trust and then to attraction but not from attraction to trust. Findings also suggested that similarity can be expected to be secondary (or even redundant) when trust is already established.