This study determined the psychometric properties of the Economics Achievement Test (EAT) using Item Response Theory (IRT). Two popular IRT models namely, one-parameter logistics (1PL) and two-parameter logistics (2PL) models were utilized. The researcher adopted instrumentation research design. Four research questions and two hypotheses were formulated to guide the study. The population size is five thousand, three hundred and sixty-two (5,362) from thirty-seven (37) schools. The sample for the study was 1,180 senior secondary school students (SSS3) drawn using multi-stage sampling procedure. The 1,180 students were stratified according to gender which resulted to 885 females and 295 males. The instrument for the study consisted of 50 multiple-choice test items on the economics achievement test, developed by the researchers. Reliability and validity for each item and for the whole test were established according to the one-parameter and two-parameter logistic models. Research question one was answered using 1PLM, while research questions two and three were answered using 2PLM IRT model. Hypothesis one was tested using t-test analysis of difference between the difficulty parameters estimated using 1PLM and 2PLM while hypothesis two was tested using Chi-square. The finding of the study revealed significant difference between the item difficulties estimated using 1PLM and 2PLM. Also the observed scores of the testees on the test items fit the 1PL 2PL models.