ABSTRACT.Peach is a temperate fruit species that is cultivated under various edaphoclimatic conditions all over the world. In Brazil, in the early 1950s, peaches were planted only in São Paulo state and in the Southern states, and the harvest period was restricted to 15 days. Currently, mainly due to peach breeding programs, it is cultivated in subtropical areas and even in high altitude tropical areas, with a harvest period of over 100 days. Knowledge of genetic, phenotypic and environmental parameters that influence characters of economic importance is crucial for guiding breeding programs. The objectives of this study were to estimate the heritability of phenological characters, to evaluate their distribution within populations, to test the possible existence of maternal effect and to evaluate the relationship of these traits with brown rot incidence (Monilinia fructicola). The study was performed in Pelotas, RS, Brazil during 2015-2016 to 2017-2018 seasons. Sixteen first generation (F1) progenies were evaluated, 10 of them being reciprocal crosses. All genotypes were cultivated in the same area, under the same cultural practices (without fungicide application). Full bloom was considered when more than 50% of flowers were open, and the harvest, when more than 10 fruits reached commercial maturity, the fruit development period being calculated by the difference between full bloom and harvest dates. Brown rot incidence was estimated by the percentage of fruits with symptoms. Broad-sense heritability estimates for full bloom date, harvest date, and fruit development period were high (95 to 98%), and narrow-sense heritabilities were medium to high (65 to 72%). A segregation study of these traits suggests a maternal effect on their heritability, mainly for full bloom and harvest date. The three phenological characters were significantly correlated, and only harvest date had a negative and significant correlation (-0.12) with brown rot incidence. © FUNPEC-RP.