Breastfeeding is extensively associated with significant benefits for maternal and child health. The World Health Organization recommends that infants be breastfed up to 24 months. The decision to breastfeed is affected by many factors. The present study aimed to assess the factors contributing to the duration of breastfeeding. An online questionnaire was applied to 351 Portuguese mothers of infants under five years old to collect data on socioeconomic, obstetric, and breastfeeding factors. Conditions that contribute to the duration of breastfeeding were information and education about the topic (p≤0.001), residence area (p≤0.001), number of children (p=0.002), duration of pregnancy (p=0.015), previous experience with breastfeeding (p≤0.001), and difficulties during breastfeeding (p=0.035). In conclusion, among the modifiable barriers which influence breastfeeding cessation, breastfeeding education and information is essential to improve breastfeeding rates. Keywords: Breastfeeding, duration of breastfeeding, literacy, infant nutrition, Portugal