The Fourth Industrial Revolution Chemistry Teachers Effectiveness Scale (4IRCTES) was evaluated in secondary schools in Southwest Nigeria to determine its item discrimination, item parameters, and model-data fit. This study utilised a descriptive survey research design and included 4,986 Chemistry teachers in the southwestern region of Nigeria, with a sample of 35 Chemistry teachers. The 4IRCTES instrument was used to collect data. Research question one focused on item discrimination using the Multidimensional Graded Response Model (MGRM) of the Item Response Theory (IRT). Research question two examined the overall model-data fit, or M2 statistic. Results indicated that the 4IRCTES items effectively discriminated between teachers with low and high effectiveness. Also, result showed that the MGRM of the IRT is the substantial model-data fit for the 4IRCTES. The study concluded that the MGRM of the IRT provided a strong model-data fit for the 4IRCTES, and that the scale effectively distinguished between ineffective and effective teachers.