[Objectives]  he mating behavior of the parasitic wasp Trichopria drosophilae and the effect of the frequency of mating of male and female wasps on offspring sex ratio was determined. [Methods]  The mating behavior of T. drosophilae was observed in a laboratory, and the various stages of this, including pursuing, courtship, early mating period, mating, as well as the duration of mating, were recorded. Furthermore, the effect of the number of mating events on the number of offspring and the life span of female adults was investigated. [Results]  The mating behavior of T. drosophilae included the following stages: Pursuing (95.45 ± 71.23) s, males gradually walking up to females; Courtship (50.47 ± 85.01) s, males shaking their wings and beginning to chase and climb onto the backs of females; early mating period, in which the male’s head extends from between the female’s antennae and the male’s antennae touch the mid-portion of the female’s antennae on both sides; mating (36.28 ± 11.03) s, the males copulatory apparatus is inserted into the females genital pore; late mating (8.95 ± 3.40) s, females drive off males by vigorously swinging their abdomen. The mating frequency of males was significantly higher than that of females; females only mate once in their lifetime whereas males can mate up to 19 (16.54 + 1.37) times (n=10). [Conclusion]  The mating behavior of T. drosophilae can be divided into distinct stages. The pursuing stage is the longest and is initiated by males which also are the most active sex during the courtship stage. The shortest stage is the late mating stage which is the only stage initiated by females. Males that mate more often produce noticeably fewer female offspring.