The aim of this study was to investigate the factorial structure and psychometric properties of the Separation Anxiety Assessment Scale (SAAS) with Spanish schoolchildren. The participants in Study 1 were 1281 children aged 8-11. Exploratory factor analysis identified four factors: worry about calamitous events, fear of abandonment, fear of being alone, and fear of physical illness, which explained 47.77 % of the variance. The participants of Study 2 were 4628 schoolchildren aged 8-11. The four related factors model was validated by confirmatory factor analysis. The internal consistency (alpha = .84) and temporal stability (r = .77) were good. The convergent validity was evident from the pattern of correlations with the measures of separation anxiety, sensitivity to anxiety and school fears. The sensitivity of the scale was 83 %, and its specificity, 93 %. The complementary subscales predicted the diagnosis of separation anxiety disorder. The results support the reliability, validity and clinical utility of the SAAS.