The formation and growth behavior of transformed ferrite with intercritical annealing time and cooling rate in a dual-phase steel was investigated. The formation of transformed ferrite in the specimen with the short intercritical annealing time, 140 sec, started when cooled to the low temperature. The temperature at which transformed ferrite initiated to form was lower at the higher cooling rate. The effect of cooling rate on the formation behavior of transformed ferrite was similar regardless of the intercritical annealing times. However, because the partitioning of substitutional alloying elements in case of the short intercritical annealing time, 140 sec, could be neglected, the growth behavior of transformed ferrite was not affected by the substitutional alloying elements.