Hydrogeochemical studies were carried out on the Dallol area (Afar region, Ethiopia) to characterize the hydrogeochemistry of the hydrothermal and Lake brines and to identify the dominant hydrogeochemical processes and mechanisms responsible for the evolution of the chemical composition of the brines. Descriptive statistics, graphical methods, correlation matrixes, hierarchal cluster analysis (HCA), principal component analysis (PCA), and PHREEQC modeling were used to gain an understanding of the hydrogeochemical facies, hydrogeochemical processes, and geochemical evolution in the study area. Dallol dome brines are characterized by very low and negative pH due to the inputs of very acidic gases such as HCl, HF, SO2, and H2S emerged from magmatic fluids. The hot springs (>100˚C) have interconnection with the magmatic body that enables it to dissolve basaltic rocks at a great depth and the overlaying evaporitic sequence during ascent. They are supersaturated with respect to halite, that precipitate first and form salt chimneys. In addition to halite, the cascading pools are supersaturated with gypsum and anhydrite due to evaporative concentration. Except for Na, Ca, Cl, and B, most of the elements show a high linear correlation with each other and increase linearly from hot springs towards the furthest pools showing evaporation dominance over precipitation. Black and Yellow Lakes are supersaturated with respect to halite, anhydrite, tachyhydrite, and kieserite. Piper plots and hierarchical cluster analyses have shown that there are three main hydrochemical facies in the Dallol area and its surrounding: namely Na-Cl type, Ca-Mg-Cl type, and Mg-Cl type. Principal component analysis revealed that the first 2 factors explain 81.32% of the total variance of the hydrochemistry. The first component, with high positive loadings in Al, Fe, Mn, P, V, Zn, is related to the dissolution of basaltic rocks by magmatic water at great depth. The second component, with high loading in Na, Ca, K, Cl, and Sr, is related to the dissolution of evaporites and subsequent evaporative concentration on the surface. The results of this study demonstrated the importance of combining graphical, multivariate statistics, and modeling to characterize the hydrogeochemistry and hydrochemical evolution of brines