Electrospray ionization mass spectrometry(ESI-MS) technique was used to find out the type of species of uranyl with a-hydroxyisobutyric acid in positive and negative ion modes. It was found that the singly charged monomeric and doubly charged dimeric species were present in soft ionization conditions. The molecular level understanding on the structures and energetics were investigated using density functional theory based calculations. It was found that ML₃, the most intense species observed in ESI-MS were energetically more favorable as compared to ML₁and ML₂.