The aim of this study was to evaluate the quality of ground and surface water resources in Brčko Distrikt of Bosnia and Herzegowina and classify them according to selected parameters, coefficients and water quality indices. The samples were collected from 92 groundwater sources during the period of five years (2004 – 2008) and three measurement profiles of the Sava River and its tributaries, Tinja and Brka, in this region during 2008 and 2009. The results showed that 83.7% of groundwater quality parameters were in accordance with the recommended WHO standard. The content of manganese, iron, ammonia and total hardness were higher than allowed. Furthermore, the SAR and RSC results clearly showed that the water from the south-eastern and central parts of of Brčko District of Bosnia and Herzegovina can be used for irrigation without any restriction, while water in the north-western part of this region with a moderate quality for irrigation should be taken into account in growing some kinds of plants. In addition, the obtained LSI, RSI, and PSI values demonstrate that all groundwaters in this region are stable and safe for industrial purposes. According to the results of multivariate analysis, all groundwater sources were divided in ten clusters that are naturally associated. Furthermore, the present work is aimed to assess the water quality index for investigated water according to WQINSF, WQIIR and WQIIN. Moreover, based on the results of factor analysis (multivariate analysis) WQIIN has been modified and a new index of quality for ground and surface water from Brčko Distrikt of Bosnia and Herzegowina, WQIB, was developed with the aim to determine the place with the best drinking water quality in the specified region. For calculating the WQIB, the following 11 parameters have been considered: pH, total hardness, TDS, F, Cl, NH4, SO4, HCO3, SAR, Fe and Mn. And finally, the map with WQIB values provides a comprehensive picture for easier interpretation and decision making in better planning and management of water resources. The developed WQIB proved to be a simple and reliable index that can be quickly and successfully applied on the assessment of ground and surface water from Brčko Distrikt of Bosnia and Herzegowina. This index has an advantage over the other because it can better highlight the adverse effects on water quality and it has a stricter rating. It can be concluded that the modification carried out was justified.