Objective: To build and validate the Patient Safety Assessment in Medication Administration (ASPAM - Avaliação da Segurança do Paciente na Administração de Medicamentos) tool. Method: Methodological study in which the construction, Content Validation Index (CVI), construct validation (factorial analysis) and reliability were performed in terms of homogeneity (Cronbach’s Alpha). Results: The ASPAM reached CVI of 0.77 for simplicity, 0.76 for clarity and 0.93 for relevance. The exploratory factorial analysis was adequate for the tool (Kaiser-Meyer-Olkim of 0.66 and Bartlett’s sphericity with p <0.001). The Cronbach’s Alpha end of the scale with 28 items was 0.85. Conclusion: The ASPAM tool was valid and reliable for the identification of risk-generating conditions for the occurrence of Adverse Drug Events.