Literature indicates that teachers and students who experience trust and belongingness in their school communities have higher levels of indicators of positive quality of life, such as performance, innovation, and creativity. Also, they are open to creating more authentic relationships and fostering an environment based on psychological safety with implications on their well-being, quality of life, self-efficacy, and their general mental health. This quantitative study aims to investigate the impact of an online training program called "Development of trust and belongingness in interpersonal relationships of school teachers" on several psychological variables related to the individual wellbeing. A number of 475 school teachers participated in the study, from several schools located in different regions of Romania. Data were collected pre- and post-intervention with an online form composed of three different questionnaires addressing the following variables: belongingness, connectedness and teacher's self-efficacy. The findings indicate significant effects of the online intervention program on all the target variables.