The study investigated the gender based comparative analysis of item parameters of geography qualifying examinations using item response theory in senior secondary schools in south west, Nigeria. The study adopted an ex-post facto research design. It examined the responses of Senior Secondary School II students who sat for the 2021 Geography qualifying examinations in Southwest Nigeria. The sample comprised 1,200 SS II students' responses to 50 multiple-choice Geography items from the Ekiti State Qualifying Examination (ESQE) and the Oyo State Qualifying Examination (OSQE), and 60 multiple-choice items from the Ogun State Qualifying Examination (OGQE). A multistage sampling procedure was employed to select the sample. Students' responses to 50 multiple-choice Geography items from the ESQE and OSQE, and 60 items from the OGQE, were obtained from the respective State Ministries of Education in the form of Optical Mark Reader (OMR) sheets. Correct responses were scored 1 while incorrect responses were scored 0. The data were analyzed using inferential statistics in line with the stated hypotheses. Item parameters for the 1-Parameter, 2-Parameter, and 3-Parameter Logistic Models were estimated using the BILOG-MG software. The hypotheses were tested using correlation analysis, t-test, Analysis of Variance (ANOVA), Levene's test, Tukey's post hoc test, and Shapiro-Wilk's test at a 0.05 level of significance. The findings showed a significant gender difference in one-parameter indices in Oyo and Ogun States, while Ekiti State differed from both. In Oyo and Ekiti, male and female examinees perceived the items as having different difficulty levels, whereas items functioned similarly across genders in Ogun. Conversely, the 2-parameter results indicated similar difficulty perceptions for both genders in Oyo and Ogun, but not in Ekiti, while vulnerability to guessing was similar across genders in Oyo and Ekiti but differed in Ogun. It was therefore recommended that item analysis be conducted by experts before final examination administration, qualified subject teachers be employed to replace those who have left service to enhance performance, and teachers be trained on item analysis and test construction to improve item quality.