The accuracy of the Life Orientation Test–Revised (LOT–R) in measuring dispositional optimism was investigated applying item response theory (IRT). The study was conducted on a sample of 484 university students (62% males, M age = 22.79 years, SD = 5.63). After testing the 1-factor structure of the scale, IRT was applied to evaluate the functioning of the LOT–R along the pessimism–optimism continuum. Item parameter estimates and the test information function showed that each item and the global scale satisfactorily measured the latent trait. Referring to the IRT estimated trait levels, the validity of the LOT–R was studied examining the relationships between dispositional optimism and psychological well-being, sense of mastery, and sense of coherence. Overall findings based on IRT analyses provide evidence of the accuracy of the LOT–R and suggest possible modifications of the scale to improve the assessment of dispositional optimism.