Statistical data indicate an increase in the social harm of violence in the form of conflict, especially among youth. Youth are the social capital of the country, and one way to reduce social harm is trust and refer to municipal social services. Research shows a decline in youth trust as a social issue. the aim of this study is to present a strategy to strengthen youth trust in Tabriz Municipality's social services using a social marketing approach. The research used a mixed-method approach in two stages. First, a qualitative systematic review was conducted. Then, Glaser grounded theory method was applied. Thematic analysis was also used to analyze the data. The statistical population in the first stage includes all articles published on trust in the municipality in the last 20 years, and in the second stage includes the youth of Tabriz, experts in the Tabriz municipality, and theoretical experts. In the second stage, Theoretical sampling was used, and data came from Unstructured interviews with 17 participants until theoretical saturation was reached. The validity and reliability of findings were confirmed using four Lincoln and Guba criteria. In the first stage, seven trust factors related to the trustee were identified. In the second stage, a promotion strategy using influencer marketing on Instagram was developed. To reach youth effectively, the institution's public relations should first segment the audience by age. Then, it can choose the best advertising method based on each segment's characteristics.