The predatory mite, Neosiulus californicus (McGregor) was released to control the two-spotted spider mite, Tetranychus urticae Koch infesting cucumber cultivars (Hisham and Fand) under greenhouses with the rates of 5 and 10 individuals/bit at average level infestation 164 and 183 mite per 20 leaves for the first and second season at Kafr Bedway district, Dakahlia Governorate. The reduction percentages of acarine mite population in cucumber cultivars Hisham and Fand were (95.26 & 91.54%) and (97.41 & 94.53%) in levels 1 and 2 in the first season, respectively, while in the second season the reduction percentages were (97.37&98.67%) and (95.18&97.13%), respectively. The above mentioned results 'indicated that the possibility of controlling 7: urticae on cucumber plants under greenhouses, by releasing N. californicus, without any damage on leaves and good production, free from pesticide residues.