Acetaldehyde (CH 3 CHO) is known as a primary carcinogen, and the development of wearable gas sensors for its detection at room temperature has rarely been rarely reported. Herein, MoS 2 quantum dots (MoS 2 QDs) have been employed to dope with poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT: PSS) via a simple in situ polymerization technique, and the CH 3 CHO gas-sensing properties of the resultant flexible and transparent film were investigated. MoS 2 QDs had been evenly dispersed into the polymer, and it was shown that PEDOT: PSS doped with the 20 wt % MoS 2 QDs sensor exhibited the highest response value of 78.8% against 100 ppm CH 3 CHO and its detection limit reached 1 ppm. Moreover, the sensor response remained stable for more than 3 months. In particular, the different bending angles (from 60 to 240°) had little effect on the sensor response to CH 3 CHO. The possible reason for the enhanced sensing properties was attributed to the large number of reaction sites on the MoS 2 QDs and the direct charge transfer between the MoS 2 QDs and PEDOT: PSS. This work suggested a platform to inspire MoS 2 QDs-doping PEDOT: PSS materials as wearable gas sensors for highly sensitive chemoresistive sensors to detect CH 3 CHO at room temperature.