The main objective of this study was to investigate the relationship between organizational practices of competencies development and turnover intentions and whether this relationship is mediated by affective organizational commitment. To this end, we hypothesized: (1) organizational practices of competencies development have a negative and significant relationship with turnover intentions; (2) organizational practices of competencies development have a positive and significant relationship with affective organizational commitment; (3) affective organizational commitment has a negative and significant relationship with turnover intentions; (4) affective organizational commitment mediates the relationship between organizational practices of competencies development and turnover intentions. The sample of this study consisted of 345 participants working in organizations based in Portugal. The results indicate that training, individualized support, and affective commitment negatively and significantly affect turnover intentions. Training and individualized support have a positive and significant effect on affective commitment. Affective commitment directly mediates the relationship between organizational practices of competencies development (training and individualized support) and turnover intentions. This study points out to Human Resources Management professionals the importance of training and individualized support in boosting affective commitment, reducing turnover intentions, and keeping the human capital that is so important for the organization’s competitiveness.