In the past two decades, there has been a growing theoretical and empirical interest on the role of shame, namely internal shame, on the conceptualization of human functioning and several interpersonal and emotional problems. The current study explores the psychometric properties of the Portuguese version of the Internalized Shame Scale (ISS), a self-report measure which assesses trait shame, composed by an Internal Shame subscale, measuring internalized shame, and a Self-Esteem subscale. The factor structure, internal consistency, test-retest reliability and convergent and discriminant validity for both subscales, are presented, in a sample of 385 college students. The Principal Components Analyses reveal that both Internal Shame and Self-Esteem subscales present a one-dimensional structure which explains, respectively, 48.54% and 57.7% of the variance. The subscales present high internal consistency, with high Cronbach'alphas (.95 and .85) and moderate to high item-total correlations. The two subscales present an excellent temporal stability. Convergent and discriminant validity of the subscales was corroborated through the moderate correlations with a measure of shame and of social comparison, and through the low and moderate correlations with the subscales depression, anxiety, and stress. The Portuguese version of the ISS is a valid and reliable instrument to measure internalized shame.