Today, maintaining and strengthening customer loyalty has become a strategic challenge for organizations. Customer loyalty is more important in service industries such as the insurance industry than in other industries. According to studies, the long-term relationship between the customer and the organization depends on the level of customer trust. If customers trust the organization, they will be more engaged in the organization's products and services. Therefore, the present study was conducted to investigate the effect of trust on customer loyalty through the mediator role of customer engagement. The statistical population of the study included customers of Iran Insurance branches in Mashhad city. 384 people participated in this study by Non-random sampling available. The data collection tool was a standard questionnaire. The content validity of the questionnaire was confirmed by experts, the structure validity of the questionnaire was confirmed by factor analysis and the reliability of the questionnaire variables using Cronbach's alpha coefficient. Data were analyzed using SPSS 24 and Smart PLS 2 softwares and structural equation modeling method. The findings indicated that Customer trust has a positive and significant effect on brand loyalty and customer engagement with brand. Customer engagement with brand has a positive and significant effect on brand loyalty. The mediating role of customer engagement with brand in the relationship between customer trust and brand loyalty was also confirmed.