Abstract This chapter discusses nanocomposites based on carbon nanotubes (CNTs), metal oxides (MOXs), and CNT/polymer-based textile sensors for gas sensing applications. This chapter first reviews the historical background of the MOX, the hybridized MOX/CNT composite gas sensors, and the CNT/polymer-based wearable textile gas sensors. It then describes several popular methods for preparation of MOX/CNT sensing films and CNT/polymer film–based textile gas sensors such as spin-coating, drop-coating, screen-printing, dip-coating, immersion coating, and electron beam evaporation techniques. The ways to characterize MOX/CNT materials and CNT/polymer composite materials with their basic theories including Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy are presented. Finally, the sensing mechanism of an MOX/CNT gas sensor–based on p–n heterojunctions and CNT/polymer-based textile gas sensors is highlighted.