The purpose of this research is to determine the effect of Marketing Mix (Product, Price, Place, and Promotion) and service to the customer’s decision to use the product “Tabungan BSM” in Bank Syariah Mandiri branch office Kaliurang. The results of this research can be taken into consideration of the bank’s management to evaluate marketing strategies and services applied in the bank. The sample in this research is 112 respondents from customers “Tabungan BSM” in Bank Syariah Mandiri branch office Kaliurang. The sampling technique uses purposive sampling method. This research is a field research with quantitative approach. The data are primary and secondary. Primary data is obtained based on respondent’s answers to a quesionnaire distribution. This research uses multiple regression analysis with the normality test, classical assumption test, descriptive analysis, F test, coefficient of determination test, and hypothesis test (t-test) with processing using SPSS 17.0 for Windows. The data processing results are obtained equation Y = 2,279 + 0,062X1 + 0,246X2 + 0,173X3 + 0,356X4 + 0,157X5 + e. Based on Ftest shows that Fhitung (12,962) > Ftabel (2,300) and the level of significance probability of 0.000 (the level of significance probability) is smaller than 0.05, then the regression model in this reseach can be used and jointly independent variables influence the decision of used “Tabungan BSM”. Based on coefficient determination test is known that Adjusted R2 value is equal to 0.350 or 35%. This means that with five independent variables that include Product, Price, Place, Promotion, and Service can represent 35% of variables which affects the descision variable usage of “Tabungan BSM” by customers of Bank Syariah Mandiri branch office Kaliurang, while the rest (100% - 35% = 65%) is explained by other variables outside the model used. Meanwhile, based on the t-test, it shows that the variables of product, price, Place, and servicedo not affect the customer’s decision to use “Tabungan BSM” in Bank Syariah Mandiri branch office Kaliurang. There is only one variable that is variable Promotion.