Background: Citrullus colocynthis (CC) is an herbal medicine used in the treatment of a wide range of diseases. Recently, It has been studied on in vitro activation of mice sperms with no research concern the effect of this plant on the DNA normality following in vitro preparation of human semen samples. Objectives: The present study was aimed to examine the effect of adding CC in the medium used for in vitro sperm activation of asthenospermic men and related factors and to found out the effect of CC on the DNA status following the activation. Materials and Methods: Citrullus colocynthis aqueous extract (0.01mg/ml culture medium) was used for in vitro sperm activation . One hundred and ten semen samples were divided into two groups, the first group activated in vitro by adding CC extract to the culture medium Ham's F-12 (the treated group) and, the second group sperm activated in vitro with Ham's F-12 alone ( the control group). Results: In vitro activation of sperms with aqueous extract of CC has shown positive effect on sperm concentration, sperm motility, and grade activity of progressive forward movement. There was a significant (P<0.05) increase in certain sperm function parameters of asthenozoospermic in treated group compared with the control group .The study showed that the DNA fragmentation resulted from treated group were lower than that of control group. Conclusions: According to the results of present study, adding aqueous extract of CC to the human sperms activation culture medium leads to an improvement in certain sperm function parameters of asthenozoospermic men with no harmful effect on the human sperms DNA with decrease in DNA denaturation.