Background: Coccidiosis is recognized as the parasitic disease that has the greatest economic impact on poultry production. Modern poultry production is largely dependent upon anticoccidials. Objectives: The aim of the present study was to determine and compare the efficacy of two chemical anticoccidials (Clopidol and Diclazuril) on oocyst shedding and their probable effects on growth performance and feed efficiency of broilers in experimental coccidiosis. Methods: One hundred and twenty Ross 308 one day old broilers were randomly assigned into 4 groups: CON+, infected with Eimeria mixed oocysts but not medicated; CON-, not infected and not medicated; CLO, infected and medicated with Clopidol; DIC, infected and medicated with Diclazuril. Chickens in all groups except negative control were inoculated by mixed sporulated oocysts of pathogenic Eimeria at the end of the 3rd week of age. Oocyst shedding was counted using a Mc Master counting chamber. Body weights, body weight gains, and feed conversion ratio were determined on weekly basis. Results: Obtained results showed that Diclazuril was more effective in reducing oocyst shedding than Clopidol. As expected, mean body weight in the positive control group was lower than other groups. But surprisingly, no significant difference was found between Diclazuril or Clopidol treated birds and positive control group, at the end of the experiment. In comparison of weight gain in different treatment groups except for the 4 and 5th week, no significant difference was found in different groups. In the last week of the experiment, difference in weight gain between groups was not significant. According to feed conversion ratio (FCR)  results, anticoccidial supplementation did not have any significant effect on improving FCR. ConclusionS: It is reported that some anticoccidials reduce feed consumption and feed conversion. It seems that neither of the present synthetic anticoccidials is completely satisfactory in controlling coccidiosis economic losses and new strategies are urgently required.