The present study was performed to evaluate the role of Aloe vera L. leaf extract (AvLE) on some physiological and cytogenetical parameters of Allium cepa L. seeds exposed to salinity. The radicle length of the seeds germinated in the medium with AvLE alone increased as compared with ones of the control seeds germinated in distilled water medium, while their radicle number and fresh weight reduced according to the control. In addition, the germination percentage of the mentioned seeds statistically was the same as the control seeds. Furthermore, the seeds germinated in the media containing 0.1 mg/L AvLE alone showed a significant increase of mitotic index, although they exhibited a higher number of chromosomal aberrations and micronucleus (MN) formation as compared with the seeds germinated in control conditions. On the other hand, salt stress considerably inhibited the seed germination and seedling growth of A. cepa. Moreover, salinity markedly decreased the mitotic index in root tip meristems of the seeds and increased the number of chromosomal aberrations. The negative effect of salt on the seed germination, seedling growth, mitotic activity and MN formation was alleviated in dramatically varying degrees by AvLE application. In contrast, the detrimental effects of salt on the chromosomal aberrations greatly increased with this treatment. Consequently, we reported that the application of AvLE alone induced chromosomal aberrations and MN formation, which are an indicator of genotoxicity, and had cytotoxic activity in normal conditions. However, the frequency of MN is greatly reduced in root tip cells of the seeds germinated in the medium containing 0.1 mg/L AvLE +0.15 M NaCl.