The objective of this study was to translate and psychometrically assess a Portuguese version of the Breastfeeding Self-Efficacy Scale-Short Form (BSES-SF). The original English version of the BSES-SF was translated to Portuguese and tested among a sample of 89 mothers in southern Brazil from the 2nd to 12th postpartum week followed by face-to-face interviews. The mean total score of the Portuguese version of the BSES-SF was 63.6 +/- 6.22. The reliability analysis of each item in the scale attained significant Cronbach's alphas of 0.63 or superior. The Cronbach's alpha generated by the entire range of 14 questions was 0.71. A factor analysis identified one factor that contributed to 20% of the variance. This study demonstrates that the original English version of the BSES-SF was successfully adapted to Portuguese. The Portuguese version of the BSES-SF constitutes a reliable research instrument for evaluating breastfeeding self-efficacy in Brazil.