The purpose of this mixed methods sequential explanatory study was to analyze the contributions of school climate dimensions and teachers’ professional identity elements to building teachers’ overall professional capital. For this purpose, correlational research and case study designs were employed in quantitative and qualitative phase, respectively. Quantitative data was collected from randomly selected 379 teachers using close-ended questionnaire, while qualitative data was collected from eight purposefully selected teachers using semi-structured interviews. The quantitative data was analyzed using descriptive statistics, Pearson correlation, EFA, CFA, SEM, and mediation analyses, whereas the qualitative data was analyzed thematically. Relationships within school and professional learning and teaching climate fully mediated the contribution of school leadership and institutional environment, and partially mediated the contribution of institutional safety to teachers’ professional capital development. Relationships within school and professional learning and teaching climate had strong direct contribution to building teachers' professional capital that explained 74% variance. Self-efficacy partially mediated the contribution of engagement in individual and collaborative professional learning, while job satisfaction partially mediated the contribution of internal and external motivation to become a teacher to teachers’ professional capital development. Self-efficacy and job satisfaction fully mediated the contribution of perception of teaching. Self-efficacy, job satisfaction and engagement in collaborative learning appeared to have a significant direct contribution, which explained 88% variance on professional capital. In conclusion, relationships, professional learning and teaching climate and institutional safety as well as self-efficacy, internal motivation to become a teacher, engagement in collaborative professional learning and job satisfaction were found to be important predictors of teachers’ professional capital development. To this end, future research needs to validate measurement and structural models in different school contexts and by using multilevel and multi-group analyses approaches.