The research investigated whether teachers' participation in decision-making (PDM) contributes to the development of affective trust during school reform over time, or vice versa. A model including principals' interpersonal skills was tested during implementation of the organizational reform. Teachers (n = 1,482) from 113 Israeli elementary schools participated in the first measurement, and 1,390 teachers from 106 of these schools participated in the second measurement. A cross-lagged design for 2 years showed that PDM leads to affective trust over time. Furthermore, PDM mediated the relationship between principals' interpersonal skills and affective trust over time.