The study focused on development and item response theory calibration of economics achievement test for secondary school students in Plateau State, Nigeria. What motivated the study was the persistent poor performance of students in external examination in the subject which could be attributed to the quality of teacher-made test that is used in assessing students’ achievement in the subject. Apart from the quality of teacher-made test that is used in assessing students’ achievement, some teacher-made test used by teachers are developed using classical test theory with its attendant shortcoming of being sample dependant and test dependant. Again there is no standardized achievement test that can be used by teachers for continuous assessment of students’ achievement in the subject in the study area and hence the need for this study. The designs of the study were instrumentation and cross-sectional survey research design. The population of the study consisted of all the 23712 SS 2 and a sample of 1454 from the population economics students was used for the study. Multistage sampling technique was used for the study. Multistage sampling technique was used to ensure that adequate number of students was selected from each zone, local government, schools and students. A sample of 134 schools, made up of 74 private schools and 60 public schools, 68 from rural and 66 from urban, 720 males and 734 were selected. The instrument for data collection was Economics Achievement Test (EAT) developed and calibrated by the researcher. Six research questions were raised to guide the study. The research questions were answered using difficulty indices, discrimination indices and guessing parameter indices. The validity of the instrument was established using test blue print and the judgement of experts from Economics Education and Research, Measurement and Evaluation. The reliability of the instrument was established using omega reliability procedure and it was found to be 0.83. The results of the findings indicate that the test was valid, reliable and a multidimensional test. That had moderate difficult items. The test was recommended to be used by teachers in conducting continue assessment of economics students in Plateau State Nigeria.