Relationship marketing involves strategies that focus on developing and strengthening long-term, mutual relationships with customers, which can have significant positive impacts on brand image. In present study, brand image, as a key element in companies' marketing strategies, plays a crucial role In purchasing choices, loyalty and finally customer engagement. This study aims to the effect of relationship marketing on brand image mediated by brand equity. The present study is applied in its purpose And according to the type, the nature of the problem, the purpose and the research hypotheses of the type of descriptive research from the correlation branch, and survey-based in terms of data collection. The statistical population consists of Digikala's customers in Mashhad, numbering 496 people and the sample size was selected by simple random sampling method and 284 people were selected as a sample using Cochran's formula. To collect the research data, three standard questionnaires were employed: the Morgan and Hunt (1994) questionnaire to measure relationship marketing, the Aaker (2012) questionnaire to assess brand image, and the Delgado (2005) questionnaire to evaluate brand equity. The validity of the questionnaires was confirmed through content validity and structure validity, and their reliability was verified using Cronbach's alpha coefficient. Data were analyzed using structural equation modeling (SEM) with SPSS and AMOS software. The findings demonstrate that relationship marketing positively and significantly affects on brand image and brand equity. Furthermore, brand equity positively and significantly impacts on brand image. Also, considering that the significant indirect effect of relationship marketing on brand image, the mediating role of brand equity in the relationship between relationship marketing and brand image is confirmed.