Background Breastfeeding care plays a fundamental role in establishing breastfeeding and longer duration after discharge. Practices though vary among professionals involved and are often inconsistent with good practices recommended, being a threat to women's breastfeeding self-efficacy. Breastfeeding self-efficacy is considered a predictor for successful breastfeeding and a significant variable amenable to intervention for promoting lactation Aim To evaluate the efficacy, feasibility and acceptability of a new breastfeeding self-efficacy promoting programme (SIALAC) on 6-month breastfeeding maintenance. Methods In this exploratory multi-centre controlled trial, participants were allocated into control and intervention groups sequentially. Professionals in charge of the treatment groups were trained in between, with an especial focus on reducing practice variability. Control and intervention group women received usual care, and the intervention group received in addition SIALAC, a three-stage breastfeeding self-efficacy promoting programme. Primary outcome was breastfeeding maintenance up to 6 months analysed by Kaplan-Meier and Cox proportional hazard regression analysis. Student's t-test or chi-square tests were also used for continuous and categorical variables. Data on breastfeeding status and breastfeeding self-efficacy were collected at baseline, and 4, 8 and 24 weeks after birth. Results From May 2014 through November 2015, participants were enrolled. The sample consisted of 112 women. No relevant socio-demographic or obstetric difference was found between groups. The intervention achieved a significant difference between groups in breastfeeding survival (X-2 = 4.94, p = 0.026). Six-month breastfeeding maintenance was significantly higher in the intervention group (67% vs. 55%; X-2 = 5.384, p = 0.020). Breastfeeding dropout in the control group was 3.3 (CI 1.1, 10.1) times higher than that of the intervention group at 6 months. Breastfeeding self-efficacy scores were higher in the intervention group although without significant statistical difference. The programme showed good acceptability. Conclusion Breastfeeding self-efficacy promoting programme SIALAC was beneficial in fostering 6-month breastfeeding survival. Full-scale trial should consider feasibility-related issues identified.