Populations of Acacia tortilis (Forssk.) Hayne subsp. tortilis were monitored in South Sinai, Egypt. Age determination was mainly based on canopy volume and stem circumference. Study sites were located in wadi systems in the upstream, midstream and downstream of the wadis. The upstream populations are represented in all size class distribution, while populations in the midstream and the downstream parts have one or more size classes missing due to the variation of water income and human impacts. Phenological monitoring showed that the appearance of new leaves started in December-January. Leaf shedding reaches its peak during November. A. tortilis has two flowering events. The first flowering event begins on old branches in March followed by peak fruiting in May. The second flowering event begins on the new branches in July followed by peak fruiting in September-October. Life table analysis and fecundity schedules showed that the flowers, seeds and seedlings are the shortest stages in the life span. The net reproductive rate was 0.281, the estimated intrinsic rate of increase reached -0.00337 per capita per year and the average generation time of the species attained about 380 years. Population demography, phenology and life table analyses draw the attention towards specific conservation considerations to manage the species population in the protected and nonprotected sites.