The study was aimed to investigate the growth, instability and decomposition of onion in Maharashtra. The data of area, production and productivity of onion pertaining to 30 years (1989-90 to 2018-19) were made available through the secondary source of NHRDF which was further analysed using exponential function, Cuddy Della Valle’s Index and decomposition analysis model. The results of the study disclosed that, there was positive and significant growth of area, production and yield of onion during overall study period with annual growth rates of 8.43 per cent, 9.36 per cent and 0.85 per cent, respectively. There was high instability during overall period for area and production while, productivity showed a stability with low instability value of 12.89 per cent. The decomposition analysis indicated that the area under onion cultivation played an important role for the rise in production of onion with 62.80 per cent of area effect, 4.97 of yield effect and 32.21 per cent of the interaction effect during overall study period. The results of decomposition analysis have important policy implications because each growth component alone has a limited scope to expand overtime. There is need for horticulturists, breeders and entomologists which are working in the SAU and ICAR institutes to pay attention and find some technological breakthrough to increase the productivity of onion in the state.