Recent research has suggested that teachers' burnout is growing and, consequently, affecting their overall satisfaction with life and professional involvement. The goal of this study was to assess burnout in Portuguese teachers and to explore whether burnout levels are associated with teachers' personal and professional characteristics. A sociodemographic questionnaire and the Oldenburg Burnout Inventory (OLBI) were used to collect data from a sample of 262 teachers, who were mostly female (66.0%), were aged between 26 and 63 years (mean = 44, SD = 7.95), and had an average of 18 years of experience in teaching regular classes (SD = 9.22) and an average of 2 years of experience in special education (SD = 4.97). The results suggested the adequate psychometric properties of the OLBI in Portuguese teachers. Moreover, the older the teachers were, the higher the levels of burnout they reported. Burnout was positively associated with the number of years of experience but only in regular education teachers. Although no differences in burnout as a function of experience in inclusive classrooms were found, a positive correlation of teachers' burnout with the number of students with special needs in the classroom was identified. The results are discussed according to the literature, and suggestions for future studies are presented.