The present study has been carried out to investigate the effects of an acaricide Fenazaquin on seed germination, shoot-root growth, total carbohydrate, free amino acid, protein content, mitotic division, chromosomal aberrations and micronuclei in barley (Hordeum vulgare L.). Presoaked seeds of barley were treated with various concentrations of fenazaquin viz. 25, 50, 100 and 200 ppmfor 6, 12 and 24 hr. The treated seeds were washed thoroughly with running tap water and allowed to germinate on moist filter paper in Petri dish at 25±1 C. After 120 hr, germination, growth, biochemical content and cytogenetic damages were analysed. The results showed except total carbohydrate content all the treated samples exhibited significant (P<0.05; P<0.01) reductions in seed germination, shoot-root growth, total protein, free amino acid content, mitotic index and increases in chromosomal aberrations and micronuclei. These remarkable findings suggest that the acaricide fenazaquin may cause potential toxic effects on the physiomorphology, cell division and genetic materials of barley.