The study included 721 patients with 12 types of malignant tumors treated at the First Affiliated Hospital of Dali University from November 2020 to May 2022 and a control group of 100 healthy individuals undergoing physical examinations during the same period. Basic information and serum samples were collected, and ELISA was used to detect the presence of anti-Toxoplasma gondii IgG and IgM antibodies in the serum samples. Statistical analysis was performed using SPSS 26.0 software. The results showed that among the 721 patients with malignant tumors, the breakdown by cancer type included lung cancer (94 cases), rectal cancer (90 cases), breast cancer (92 cases), colon cancer (69 cases), stomach cancer (74 cases), liver cancer (63 cases), thyroid cancer (60 cases), bladder cancer (40 cases), cervical cancer (30 cases), endometrial cancer (31 cases), esophageal cancer (43 cases), and prostate cancer (35 cases). There were 418 male cases and 403 female cases, with an average age of (57.27 ± 12.23) years. A total of 361 cases were of the Han ethnic group and 460 cases were of the minority group. Three hundred and twenty-four cases were from urban areas, while 497 cases were from rural areas. The positivity rate of anti-T. gondii antibodies in malignant tumor patients (32.04%, 231/721) was significantly higher than that in the control group (13.00%, 13/100) (χ² = 14.14, P ˂ 0.01). The positive rate of anti-T. gondii IgG antibodies (21.22%, 153/721) were higher than that of healthy controls (8.00%, 8/100) (χ² = 9.74, P < 0.05). There was no statistically significant difference in the positive rate of anti-T. gondii IgM antibodies (10.82%, 78/721) compared to healthy controls (5.00%, 5/100) (χ² = 2.57, P > 0.05). The positive rates of anti-T. gondii IgG antibodies in patients with lung cancer, rectal cancer, breast cancer, colon cancer, stomach cancer, liver cancer, thyroid cancer, bladder cancer, and cervical cancer were 21.28% (20/94), 22.22% (20/90), 17.39% (16/92), 26.09% (18/69), 25.68% (19/74), 19.05% (12/63), 21.67% (13/60), 25.00% (10/40), 26.67% (8/30), respectively, which were higher than those in the healthy control group of 8.00% (8/100) (χ² = 6.92, 7.63, 3.86, 10.26, 10.14, 4.38, 6.14, 7.37, 5.82; P ˂ 0.05). There was no significant difference in the positive rate of anti-T. gondii IgG antibody between other cancer types and the control group (P > 0.05). The positive rate of anti-T. gondii IgM antibodies were the highest in patients with breast cancer at 18.48% (17/92), which was significantly higher than that in the control group of 5.00% (5/100) (χ² = 8.58, P ˂ 0.05). There was no significant difference in the positive rate of anti-T. gondii IgM antibody in other types of cancer compared with the healthy control group (P > 0.05). Among 12 different types of malignant tumor patients, cervical cancer patients had the highest anti-T. gondii IgG positive rate at 26.67% (8/30). The positive rate of anti-T. gondii IgM antibody in breast cancer patients was 18.48% (17/92). However, there was no statistically significant difference in the positivity rates of anti-T. gondii IgG and IgM antibodies among different cancer (χ² = 3.96, 11.26, P > 0.05). The positive rate of T. gondii serum in patients with malignant tumors in Dali is higher than that in healthy individuals. It is recommended that T. gondii testing be conducted alongside cancer treatment.