This research aimed to analyze the factors influencing the budgetary slack. The variables consist by intervening variable, independent variables and dependent variable. The intervening variable used in this study was opportunistic behavior and supported by specific investment by supplier and uncertainty.  The independent variables used in this study were ethic, organizing commitment, meanwhile, the dependent variable included the budgetary slack. This study applied a survey method using questionnaries distributed to the the member of Dewan Perwakilan Rakyat Daerah (DPRD) region Daerah Istimewa Yogyakarta (DIY) that is DPRD Provinsi DIY, DPRD Kota Yogyakarta, DPRD Kabupaten Sleman, DPRD Kabupaten Bantul, DPRD Kabupaten Gunung Kidul and DPRD Kabupaten Kulon Progo. The total number of respondents was 88 member of DPRD. The statistical tool for testing the hypothesis was multiple regression with Smart PLS 2.0 M3 software. The results showed that the specific investment by supplier and uncertainty variables had a significant influence on the opportunistic behavior, like the opportunistic behavior and organization commitment variables had a significant influence on the budgetary slack, while ethic variable does not significantly affect on the budgetary slack. 
Keywords: specific investment by supplier, uncertainty, opportunistic behavior, ethic, organizing commitment and budgetary slack