Teacher job satisfaction and well-being have a significant impact on educational outcomes, considering that teaching is the main objective of the educational process. The aim of this study is to examine the relationship between teacher job satisfaction and four main categories of determinants: self-efficacy, relational aspects (colleague collaboration, student behavior, school management), work-related aspects (administrative workload, teaching tasks), and working conditions, in order to identify various implications for teachers’ well-being. The study employs a survey delivered to 658 K-12 (pre-university) teachers, from the North-West region of Romania. We used factorial analysis and a structural equation model to test eight proposed hypotheses. The results showed that self-efficacy, promotion, positive student behavior, and working conditions have significant effects on job satisfaction. These factors influence job satisfaction and well-being in the teaching profession because they ensure a positive work environment in which teachers and students thrive, thus leading to higher levels of involvement from teachers, students, and parents alike. An efficient work environment decreases attrition, burnout, emotional exhaustion, and teacher turnover, while increasing job satisfaction, well-being, and teacher retention.