The assessment of groundwater vulnerability to pollution has proved to be a useful tool to delimitate zones affected by groundwater contamination. For this reason, development of groundwater vulnerability maps became a useful tool for protecting groundwater resources from pollution. The Smar aquifer belongs to maritime Djeffara (southeastern Tunisia); it is essentially occupied by agricultural areas characterized by an intensive use of chemical fertilizers. The vulnerability mapping was performed by using (i) DRASTIC method (intrinsic vulnerability) that takes into account seven parameters and (ii) Susceptibility Index (SI) method (specific vulnerability) that considers five parameters. The results show that the study area is classified into three classes of vulnerability: low, medium and high for the two methods with an uneven spatial distribution. Most of the study area belongs to the class of medium vulnerability (74% and 46% of the total area for the DRASTIC and SI methods, respectively). Indeed, the validation of DRASTIC and SI models with nitrates values revealed correlation coefficient values of about 61% and 73%, respectively. The comparison between the two methods shows that the SI method is more significant for the study area. Hence, these maps could serve as a scientific basis in groundwater management.