Résumé : Background: Despite numerous advantages of breastfeeding, in Democratic Republic of the Congo, the rate of children exclusively breastfed up to six months remains low. The lack of breastfeeding support received by mothers from health care providers is an important factor of early cessation of breastfeeding. This study aimed to evaluate the effect of the training of health care providers, in the Baby Friendly Hospital Initiative, on the duration of exclusive breastfeeding (EBF) in Kinshasa. Methods: A total of 422 mothers, recruited during the first antenatal care visit in 12 maternities and followed up to six months after delivery, were included in a cluster randomized trial. In the experimental group, health care providers were trained using the "20-Hour Course For Maternity Staff". Cox proportional hazards model was used to determine the effect of the intervention on the duration of EBF. Results: The rate of EBF at six months was 2.8%; the median duration of EBF was 10.9 weeks (IQR 4.3 to 14.9). The hazard of discontinuing EBF before six month was 1.4 times higher in the control group (adjusted HR [95%CI]. = 1.40 (1.10-1.78), P= 0.007). Conclusion: In this study, training of health care providers in the Baby Friendly Hospital Initiative was associated with a significant improvement in the duration of EBF. Extending this training to different maternities could improve the coverage of EBF in Kinshasa.