Fruit growing contributes to Brazilian socioeconomic growth, both as a source of food for the population and in the generation of employment and income. However, the production chain incurs significant negative impacts, mainly due to post-harvest losses. The objective of the current study was to estimate the post-harvest losses of fruits, occurring in the retail markets of Anapurus, Belágua, Mata Roma, São Benedito do Rio Preto and Urbano Santos (Maranhão State). The study was carried out with visits to 45 commercial establishments, and the deployment of a questionnaire regarding post-harvest losses of 12 fruits. It is concluded that, in decreasing order, losses were: avocado (11.76 ± 0.09%) > papaya (11.65% ± 0.02) > banana (10.82 ± 1.75%) > grape (10.08 ± 0.06%) > passion fruit (9.28 ± 0.04%) > pineapple (8.62 ± 0.04%) > watermelon (8.48 ± 0.05%) > mango (8.00 ± 0.18%) > orange (7.12 ± 0.10%) > apple (6.68 ± 0.07%) > pear (6.52 ± 0.03%) > melon (4.32 ± 0.01%). Physiological disorders were the main cause of losses, with estimated losses being up to 10.62%. It is suggested that losses could be reduced with: better hygiene in commercial environments, effective planning of the quantities offered, and the adoption of low cost technologies for the conservation and refrigeration of temperate fruits. Some public initiatives, such as the increase in availability of training courses, improvement of roads in the rural areas of the Chapadinha Microregion, and encouragement of the expansion of fruit growing in Maranhão, may lead to improvements, with direct benefits to society in general.