This paper discusses the effect of relative humidity during storage on seed longevity and sowing depth on germination of Prosopsis africana (Guill and Perr.) Taub seeds. Freshly collected and two-years old seeds were used for this experiment. Six levels of relative humidity (RH) values ranging from 22 and 100% were obtained by using water and saturated solutions of some chemicals in closed chambers at a temperature of 28 – 30°C. Sundrying did not change the initial moisture contents of fresh seed, while RH of 0 – 22% and 72.5 – 100% degraded the seeds resulting in a rapid loss of viability. Complete loss of viability occurred within 18-21 months at low RH regimes and 9-15 months at high RH regimes. Germination and emergence of seedlings were significantly favoured when seeds were sown at a sowing depth range of 2.6 cm.