The present study was undertaken to examine the relationship between mindfulness, personality traits, and academic optimism among teachers. The research method was descriptive, correlational. The statistical population of the study included 900 student teachers of Shahid Rajaee Teacher Training University. For the purpose of sampling, purposeful sampling was used and 148 teachers were selected. The instrumentation comprised School Academic Optimism Scale, Toronto Mindfulness Scale as well as Neo Personality Inventory. The obtained data were analyzed via descriptive (mean, percentage, frequency, Pearson correlation) and inferential statistics (stepwise regression). Results showed that there was a significant relationship between academic optimism, personality traits, and mindfulness among teachers. Mindfulness and teachers’ personality traits could totally predict 24 percent of teachers’ academic optimism. Due to the impact and importance of teachers’ academic optimism as a determining structure in predicting students’ achievement and promoting teaching-learning process, it is important that due attention be paid to the personality traits of teachers as a vital criterion in the selection and evaluation of teachers.