Objective The study was aimed at investigating the association between postpartum women’s breastfeeding self-efficacy levels and their depression levels, social support levels, and breastfeeding attitudes in early postpartum period. Methods The cross-sectional study was carried out in Kirklareli in Turkey. The population of the study consisted of 398 women aged 15–49 in the first 42 days of the postpartum period who presented to eight family health centers. The study data were collected face-to-face using the Personal Information Form, Breastfeeding Self-Efficacy Scale-Short Form (BSES-SF), Edinburgh Postnatal Depression Scale (EPDS), Multidimensional Scale of Perceived Social Support (MSPSS), and Breastfeeding Attitudes of the Evaluation Scale (BAES). Results The mean age of the participants was 28.61±5.72 (Min:18, Max: 44), and the mean score they obtained from the BSES-SF was 55.13±8.39. Statistically significant differences were detected between the participants’ BSES-SF scores and age groups, employment status, perceived income level, and the number of living children (p 0.05). In the multivariate regression analysis adjusted according to the sociodemographic characteristics, BAES, EPDS and MSPSS accounted for 48.3% of the BSESSF. A negative association was found between BSES-SF scores and EPDS scores (β = −- 0.178, 95% CI:−0.349, −0.006), and a positive relation between the BAES scores (β = 0.194, 95% CI: 0.163, 0.226) and the MSPSS scores (β = 0.114, 95% CI: 0.037, 0.191). Conclusion As the level of depression of women increases in the postpartum period, the level of breastfeeding self-efficacy decreases. The breastfeeding self-efficacy increases as the level of social support increases and as the attitudes that drive breastfeeding behavior change positively.