Carob tree (Ceratonia siliqua L.) is an evergreen endemic species found naturally in Al-Jabal Al-Akhdar region which is located immediately south of the coastal belt in the northeastern region of Libya. The aim of the study was to investigate the effect of altitude on seed germination of C. siliqua. Seeds were collected from three different areas of Al-Jabal Al-Akhdar (Al-Aslab, Wadi Al-Kouf and Raas Al-Trab) with different altitudes (63, 360, and 669 m a.s.l., respectively). Mechanical scarification with soakng in distilled water treatment was used for the germination tests. Five replicates of 10 seeds from each region were placed inside a plant growth chamber and arranged in a completely randomized design. Germination parameters (germination percentage G%, mean germination time MGT and seedling length) were recorded. G% and seedling height were significantly decreased with the increased elevational gradients. In contrast, a slower rate of germination (i.e. high MGT) was observed at the higher altitude (Raas Al-Trab) region. The use of seeds from lower altitudes should be considered for seedling production of Libyan carob due to their higher germination potential.