Gratitude was an important missing factor in the extant relationship quality and relationship loyalty model. We introduced gratitude into the model of relationship quality and relationship loyalty. Two hundred and eighteen teachers from elementary schools in Taiwan were used to conduct an empirical research. The results show that teachers' gratitude has positive direct effects on teachers' trust, satisfaction and commitment. Teachers' trust has no significant effect on behavioural loyalty but has a significant effect on attitudinal loyalty. However, teachers' satisfaction has no significant effect on attitudinal loyalty but has a significant effect on behavioural loyalty. Teachers' commitment has a significant effect on behavioural and attitudinal loyalty. The mediating role of commitment implies that it (1) partially mediates the relationship between teachers' trust and attitudinal loyalty, and fully mediates the relationship between teachers' trust and behavioural loyalty; (2) partially mediates the relationship between teachers' satisfaction and behavioural loyalty, and fully mediates the relationship between teachers' trust and attitudinal loyalty.