Vachellia karroo is an important pasture legume which fixes nitrogen through its symbiotic relationship with rhizobia. Thirty two indigenous rhizobia were isolated from four different morphotypes of V. karroo obtained from four agroecologically diverse areas of South Africa. Phenotypic characterization of isolates revealed that they have the same colony morphology. Numeric analysis of the isolates' phenotypic characteristics produced six clusters at 83% level of relative similarity. High variation of the isolates growth in different temperatures, salt concentration, pH, antibiotic resistance and heavy metal resistance was also noted. Carbon source utilization was generally the same for all isolates. Isolates that tolerated a wide range of test conditions are recommended as potentially highly competitive V. karroo inoculants for use in various climatic and soil conditions.