The date palm spider mite, Oligonychus afrasiaticus McGregor (Acari: Tetranychidae), is a harmful mite pest attacking a wide range of plants worldwide. The most active natural enemy is the tiny black ladybird, Stethorous gilvifrons (Mulsant) (Coleoptera: Coccinellidae) in date palm plantations in Iran. Functional response and optimal foraging of S. governs were studied in the laboratory in order to assess the potentiality of the ladybird as a biological control candidate. The predator preference in terms of prey stage was calculated using the Murdoch model, optimal foraging hypothesis, Zero-one principal and threshold density. Results showed III and II type functional responses for the ladybird adults and larvae, respectively. Handling time estimates of adult ladybirds on spider mite adults and larvae were 0.28 h and 0.34 h, respectively, where ladybird larvae spent 0.27 h and 0.41 h for attacking the spider mite adults and larvae, respectively. Attack rates were higher on adult mite (AM) than on larval mite (LM) because the ladybird predators usually prefer largest prey. The gain rate of ladybird was also affected by different ratios of AM and LM densities in food patches. The ladybird selected food patch with the lowest number of LM. It did not completely disregard feeding on LM. © 2017, Egyptian Society for Biological Control of Pests. All rights reserved.