This research aims at finding out whether there is an influence of Communication as X1 variable and Trust as X2 variable in Relationship Marketing towards the Loyalty of the Customers of Murabahah Financing as Y variable in PT. Bank Syariah Mandiri of Banjarnegara Branch Office. The research was quantitative in nature. The research samples used were 55 respondents who were the customers of murabahah financing in PT. Bank Syariah Mandiri of Banjarnegara Branch Office. The sample collection technique used purposive sampling. The data collection technique in this research was conducted using questionnaire with Likert scale and observation. The data analysis used Double Linear Regression test and was assisted with software of SPSS 16 version 21 to process the data. The result of the research obtained shows that partially and simultaneously, Communication and Trust have positive and significant influence towards Loyalty of the Customers of Murabahah Financing in PT. Bank Syariah Mandiri of Banjarnegara Branch Office with significance value of less than 0.05 or as much as 0.004 for Communication variable and 0.000 for Trust variable.