In this study, strain ageing behaviour of dual phase steel with different martensite morphology was investigated. Three different types (Intercritical annealing, intermediate quenching and step quenching) of heat treatment was applied in the critical temperature (775 degrees C). Ageing experiments after 4 % prestrain were carried out at 180 degrees C for different times ranging from 10 to 160 min. The microstructure after different heat treatments applied to the work pieces with the network, fiber, and the bulky martesite morphologies have been identified. It was found that the martensite morphology has no effect on the trend of Delta Y (an increase in strength due to strain ageing), YS and UTS at different ageing times for 180 degrees C. However, at a given ageing time for 180 degrees C Delta Y, YS, UTS and hardness values of fibrous martensite are higher than network or bulky martensite.