Abstract: Somatic embryogenesis provides the best method for commercial micropropagation of date palm (Phoenix dactylifera L.); however, a current limitation is the lack of synchronization of developing somatic embryos. The objective of this study was to evaluate the effect of Abscisic Acid (ABA) and polyethylene glycol (PEG) combinations on the synchronization of embryo development in date palm cell suspension. Callus maintained on MS medium containing 54 μM Naphthalene Acetic Acid (NAA) and 7 μM 2-isopentenyladenine (2iP) was transferred to regeneration liquid medium supplemented with ABA at 0-100 μM and PEG at 0-15%. Maximum fresh culture weight was obtained with 10% PEG in the absence of ABA. The addition of as low as 1 μM ABA to the suspensions inhibited growth. In the absence of ABA, increasing PEG concentration increased total somatic embryo numbers reaching a maximum number at 10% PEG. Various embryo sizes differing in abundance were associated with different treatments. The highest percentage of medium size embryos, 52%, was obtained at 10 μM ABA; whereas, the highest percentage of small embryos was obtained at 50-100 μM ABA. The small embryos exhibited a state of synchronization. Although, treating suspensions with ABA and PEG affected embryo size distribution, germination was influenced by embryo developmental phase, expressed in size. Germination of 43, 63, 52 and 23% was obtained from the small, medium, large and very large embryos, respectively. Retardation of somatic embryo development caused by ABA can be further exploited to optimize culture synchronization.