The women's 400 metres T38 event at the 2020 Summer Paralympics in Tokyo, took place between 3 and 4 September 2021.

The T38 category is for ambulant athletes with cerebral palsy.

T38 athletes have the mildest form of impairment caused by cerebral palsy, often in only one limb, and not affecting the ability to run, walk or jump freely, although impairing performance.

T38 athletes may suffer minor co-ordination difficulties.

Prior to the competition, the existing records were as follows:[1] Heat 1 took place on 3 September 2021, at 21:43:[2] Heat 2 took place on 3 September 2021, at 21:51:[3] The final took place on 4 September 2021, at 20:38:[4]