The present experiment was carried out with the objective to optimize the conditions for dyeing cotton fabricwith onion peel. The collected onion peel was cleaned, shade dried, crushed into fine powder and stored in bottle to protectfrom moisture. The aqueous dye solution was prepared and the different per cent concentrations were heated for 15, 30and 45 minutes separately by constant stirring and then cooled and filtered. The dye concentration and dyeing timewas optimized based on K/s value of the dye solution. Cotton fabric was pre-mordanted with three different mordants(Al2SO4, SnCl2 and FeSO4) at 3 per cent concentration for 20 minutes and then dyed separately in optimized dye concentrationin all pH conditions. Based on the K/s value the dyeing time and pH was optimized for all the mordants separately. Thestudy revealed that, the cotton fabric pre-mordanted with FeSO4 and dyed in onion peel dye showed good colour strengthcompared to Al2SO4 and SnCl2 pre-mordanted fabric. The L* values in all the samples showed the lighter shades of colour,a* value showed colour shade towards red and b* value towards more yellow shade in all samples.