Until 2015, more than 4,000 BMT stands throughout Indonesia. And the most favorite products in demand by society is savings and financing product. One of the financing products most in demand are murobahah and musharaka financing products, while the mudharabah financing has not been too interested in the community, the data from OJK says that until January 2015 mudharabah financing products only reach 14.207 billion rupiahs, while musyarakah reached 49.416 billion rupiahs and murobahah reached 115.979 billion rupiahs. KJKS baituttamwil TAMZIS is established since 1992, which until today the deployment of branches reached 34 branches, spread across West Java and East Java. Financing in this BMT has become one of the products most in demand by customers. Every year, customers who use these products grow continuously. Until December 2014 reach IDR 148.733.047.845. Based on the case above, this study aims to determine the concept of marketing and product development of mudharabah financing in KJKS baituttamwil TAMZIS. This study is a field study. To collect data, the Researcher use the method of observation, interviews, and documentation. Then the data is analyzed using deductive to get a general concept of marketing strategy in KJKS baituttamwil TAMZIS. Then, to descriptive the method to analyze and describe the concept of marketing in KJKS baituttamwil TAMZIS. From the analysis carried out, product of TAMZIS as the main element of it's marketing mix, has an advantage of flexibility. However it has issues; (1) the lack of financial report by mudharib, and (2) the principal of TAMZIS is guaranteed. In additional, it can be concluded that KJKS baituttamwil TAMZIS are Islamic financial institution that prioritizes customer satisfaction as the axis of its marketing strategy. By doing proactive strategies or door to door strategy, that come to the members one by one into the market or members' house. Evident that this strategy is able to make customers feel comfortable and be bound by KJKS baituttamwil TAMZIS, thus indirectly establish customer loyalty towards KJKS baituttamwil TAMZIS itself. In addition to proactive strategy is a strategy ease of transaction also insurance strategies (ta'awun) which provide insurance or guarantees to the members of financing, making KJKS baituttamwil superior in the customers' view compared to other financial institutions. Finally, the researcher hopes that this paper will be useful for everyone, especially for the development of Islamic economic science. This thesis is still has a lacking, then for further research is expected to fulfill the lacking in this thesis by the empirical or other studies that can consolidate the research.