The objective of this study was to provide new insights on the egg-to-adult biological cycle and hatching rate of eggs of Haemagogus leucocelaenus, a species that transmits wild-type yellow fever in Brazil. Eggs were collected using oviposition traps, “ovitraps,” in a fragment of the Atlantic Forest in Rio de Janeiro, Brazil, in October (Experiment 1) and November (Experiment 2), 2015. Thereafter, the eggs were subjected to 16 immersions, to test hatching rate and evaluate the average development time. Hg. leucocelaenus individuals kept in a climate-controlled chamber (28° ± 1°C) showed an average development period of 10.44±0.70 d, from the start of larval stage to adulthood. Immersion viability was 49.8% and 18.2% for Experiments 1 and 2, respectively. In both experiments, the hatching peak occurred during the first immersion, where 26% and 15% of eggs hatched in Experiments 1 and 2, respectively. These results provide new insights into the biology of Hg. leucocelaenus.