The current study investigates the role of risk and trust in the Software-as-a-Service (SaaS) adoption decision. Drawing from the Web-Trust Model and Institutional Isomorphism Theory, the study proposes a multi-layered model explaining antecedents of the propensity to adopt SaaS. The model is next verified drawing from the opinions of 154 Polish IT practitioners with the Partial Least Squares (PLS) research approach. The results obtained in PLS analysis illustrate that both risk and trust directly influence the decision to adopt SaaS. However, the role of trust turned out more pronounced as trust also influences the decision to adopt SaaS indirectly through risk and, unlike risk, is also influenced by professional influence and external pressure. The findings also reveal varied importance of different types of risk for the SaaS adoption decision, highlight the paramount importance of operational risk and low significance of economic and legal risk.