Groundwater is the most important source of water supply. But, nowadays the use of groundwater for water supply in the area has been limited by increasing aquifer contamination. In general, this contamination is due to different factors such as rapid urbanization, intensive fertilizer application, industrialization and population. Auhut Plain (Afyonkarahisar, Turkey) selected to the study area is one of the most important agricultural plains of Turkey where intensive fertilizer and pesticide applications cause the groundwater contamination. Hence, the present study was carried out to develop aquifer vulnerability map for study area using DRASTIC method based on GIS. The rating coefficients of each DRASTIC parameter were determined with the aid of fuzzy analytic hierarchy process (AHP) method and mapped by GIS. In addition, the sensitivity analysis was performed to evaluate the effects of the DRASTIC parameters on the vulnerability map. According to obtained results, the computed DRASTIC vulnerability index is between 0.07902 and 0.29409. Also, groundwater vulnerability map shows that, alluvium unit has very high and high contamination potential which covers 5 and 17 % of the basin, respectively. According to single-parameter sensitivity analysis results, impact of vadose zone and net recharge parameters have the highest effective weights compared with the other parameters. In addition, the soil media parameter has the lowest mean effective weight value with 0.02 %.