Deforestation and degradation of natural forests pose a challenge for the forest sector in Ethiopia. Gathering scientific data on the reproductive biology of selected timber species has now become important to develop seed production areas and establish forest management regimes. In this regard, this study is aimed at determining the reproductive phenology of three indigenous tree species. The time of leafing, flowering, and fruiting in the three indigenous timber tree species has been recorded for three years in South West Ethiopia. This study was conducted in natural forests of the Benchi-Maji zone (Debub Bench district). We selected three prioritized species, Milicia excelsa, Antiaris toxicaria, and Pouteria adolfi-friedericii, based on the severity of their depletion and relative timber values in the area and in the country at large. Over 20 reproductively healthy, mature, and average mother trees 10 cm wide in diameter at breast height and with easily visible crowns, located at a distance of 100 m from one another, were selected out of each species and marked with marking ink. We conducted continuous observations and recorded data on leafing, flowering, and fruiting every 15 days (twice every month). The data was then analyzed using descriptive statistics. The result of this study indicates that the actual season when the seeds of Milicia excelsa are available for collection is once a year, from January to February. The results also showed that, for Antiaris toxicaria, the fruiting time is seasonal, and seeds become available for collection from early January up to the end of February. The fruiting time or the actual season when seeds of Pouteria adolfi-friedericii become available for collection is from May to June. Low-cost technologies (to establish seed production areas and domesticate the species) are recommended to be used for seed/seedling acquisition and distribution and preferable to reduce the destruction of the selected indigenous tree species.