This study attempt to analyse the size-structure of Indian manufacturing sector for the period from 2000 to 2015. Our analysis is based on both the informal and formal manufacturing sector. The data on formal sector firms are drawn from the Annual Surveys of Industries (ASI) of the Central Statistical Organisation, Government of India. For the data on informal sector firms, we relied on the Surveys of the unorganised manufacturing sector conducted by the National Sample Survey Office (NSSO) of the Government of India. We apply sampling weights provided by the ASI and NSSO to compute aggregate level information. Our findings show that there is a strong presence of informality in the Indian manufacturing sector. The majority of the enterprises and employment fall in the informal manufacturing sector even though their share of annual value addition remains less than 20 per cent over the period 2000-2015.