Tetranychus urticae Koch is the major pest of various plants worldwide. Plant compounds are known as biopesticides recently. Essential oil of the oriental arbor-vitae, Thuja orientalis was researched on repellent and oviposition inhibition of T. urticae. The LC50 values of fumigant toxicity of this oil on adults and eggs of the twospotted spider mite were 100.01 and 8.05 μl L-1 air, respectively. Also LT50 value of essential oil at 100 μl L-1 air was 2.06 h. On the other hand, all mites were killed after treatment with 1000 μl L-1 concentration. In addition, different concentrations of the essential oil of T. orientalis significantly affected oviposition deterrence and repellency of adults. The results of this study indicated that essential oil of T. orientalis may be considered as an biopesticide to control spider mites.