A heterostructure of MXene and MoS2 (Nb2CTx@MoS2) was synthesized and used for the ultrasensitive and selective detection of dopamine (DA). The composite was synthesized using a facile hydrothermal strategy and it was used to modify the carbon cloth (CC). The best composition of the material for DA detection was optimized by varying the content of MoS2 from 6.25 to 25 % while keeping the amount of Nb2CTx constant. From the electrochemical analysis, it was found that Nb2CTx@12.5MoS2 showed the best sensing characteristics owing to the optimum interaction between MoS2 and Nb2CTx. The Nb2CTx@MoS2 modified CC was able to detect DA linearly from 1 fM to 100 µM with a limit of detection (LOD) of 0.23 fM. The LOD of 0.23 fM is the lowest for DA detection in comparison with other MXene-based composites to the best of our knowledge. The developed sensor exhibited promising selectivity for determination of DA in presence of other interferents like uric acid and ascorbic acid. In addition, the developed sensor showed good repeatability, cyclic and storage stability, which shows the potential of this composite for developing flexible electrochemical sensors for the ultrasensitive and selective determination of DA. © 2023 Elsevier B.V.