Toxoplasmosis is a common infection with a complicated treatment process. Azithromycin (AZT) is a macrolide antibiotic that can be effectively used in patients with cerebral and ocular toxoplasmosis and has fewer side effects. Chlorella vulgaris (CV), a single-cell green algae that contains nutrients and has various biological effects. CV extract (CVE) has been shown to have protective effects against infections via immune enhancement by increasing the cytotoxicity of NK cells, IL-12 and IFN-gamma levels. The aim of this study was to investigate the protective effects of AZT and CV, individually and in combination, against acute toxoplasmosis in mice, and their effects on NK cell cytotoxixity, IL-12, IFN-gamma, and IL-2 levels. Six groups of mice (Balb/c) were formed. With the exception of the healthy control (HC) group, all other groups were infected with 1 ml (11 x 10(4) trofozoit/ml) Toxoplasma gondii RH strain trophozoites. No further action was performed for infected control (IC) group. After 24 hours from trophozoite infection, CVE was given to CV group, AZT to azithromycin group and CVE + AZT combination to CV + AZT group by oral gavage for 6 days. All of the mice from IC, CV, AZT and CV + AZT groups were sacrified on the 8th day of the infection and serum, peritoneal fluid and spleen samples were collected. Trophozoite count of the groups were determined in all groups except HC group and the average growth inhibition activity was calculated by using the growth inhibition formula. In all groups IL-12, IFN-gamma, IL-2 levels were measured with ELISA method and cytotoxicity of the NK cells were measured using Cytotox 96 Non-Radioactive Cytotoxicity Assay. The number of trophozoites were significantly lower in the CV group than the IC group (p<0.001), and also significantly lower in CV + AZT combination group than the AZT group. According to the growth inhibition calculations CV treatment showed 88.6%, AZT treatment 98.46%, AZT + CV combination treatment 99.4% antiprotozoal activity against T.gondii compared with the IC group. NK cell cytotoxicity in the CV and the combination group were significantly higher than all the other groups (p<0.001). IL-12 and IFN-gamma levels were highest in IC group and the lowest in AZT + CV group. This situation has been linked to the fact that the severity of the infection has fallen considerably. IL-2 levels were significantly higher in CV, CV + AZT groups than in the other groups (p<0.001). In our study, even CV administration alone caused a significant decline in infection. This may be related to the increased NK cytotoxicity, IL-2, IL-12 and IFN-g levels. CV + AZT combination seems to be an effective treatment option than AZT alone, particularly in patients who are difficult to treat with common methods or in patients with immunosuppression.