(1) Background: This paper examines the elements essential to effective teacher professional development (TPD) and the relationship between various professional environmental factors (professional learning community perceptions, self-efficacy, professional identity, principal's transformation leadership patterns), TDP in primary education schools, and TDP prediction. (2) Methods: Data were collected during the 2020 school year from 412 teachers in primary education schools in five Israeli districts. The professional learning community, self-efficacy, professional identity, transformation leadership patterns, and TPD scales were used to collect data. Descriptive statistics, Pearson moment-product correlation, and multiple regression analysis were used for data analysis. (3) Results: Overall, participants' TPD was high (4.12 ± 0.83). Statistically significant correlations were observed between TPD and four independent variables (0.41-0.64; p < 0.0001). No significant associations were seen between TPD and work-related characteristics. TPD differences were observed in participants with different educational levels (F = 4.63; p = 0.003). Higher TPD levels were predicted by perceptions of the principal's transformation leadership patterns, self-efficacy, the professional learning community, and education (F-ratio = 57.85; adjusted R2 = 0.50; p < 0.001). Conclusions: The present study attests to the importance of the school principal's leadership patterns for TPD, alongside the contribution of self-efficacy, professional learning community, and professional identity.