Although there is a growing number of studies investigating the effect of professional development (PD) on the general well-being of teachers, the reverse relationship has not been explored yet. In this respect, this paper aims to investigate the relationship between mindfulness in teaching, psychological well-being, satisfaction in life, subjective happiness, and the PD of English language instructors teaching at schools of foreign languages in various Turkish universities. Based on structural equation modeling, this paper analyzed quantitative data from 173 English language teachers to discover the relationship between these variables. Two models were tested. The first model was designed with "purpose in life" as the extrinsic variable while the second model was centered on "personal growth" for psychological well-being. The analysis of data revealed a significant positive correlation between teachers' intrapersonal mindfulness and aspects of psychological well-being, including purpose in life and personal growth, as well as subjective happiness and life satisfaction. On the other hand, the study revealed no significant relationship between intrapersonal mindfulness and attitudes toward PD. These findings highlight that while mindfulness contributes positively to individual well-being, it may not have a direct impact on attitudes toward PD. Furthermore, the research underscores the role of psychological well-being and happiness in shaping teachers' perspectives on professional growth. These insights suggest the necessity for educational institutions and policymakers to focus on enhancing teachers' psychological health as a strategy for fostering their PD. These findings contribute significantly to the understanding of the complex relationship between psychological factors and PD, offering essential implications for future research and practical applications in the field of teacher education and development.