CNT based nanocomposites are known to have superior mechanical properties, such as elastic modulus (E), tensile strength (σ), etc., compared to other nanocomposite materials. Traditionally E of the nanocomposites is measured by direct methods like the three-point bend test, four-point bend test, etc., which are destructive. However, it is possible to determine their E value by an indirect method, namely Raman spectroscopy, which is nondestructive. In this paper, four different CNT composites have been prepared, such as CNT-SiO2, CNT-NiO, CNT-NiMgAl, and CNT-NiOFe by pyrolyzing waste plastic with SiO2, NiO, NiMgAl, and NiOFe catalysts, respectively. The prepared CNTs are multiwall types with diameters and the number of walls are in the range of 4.88–108 nm and 5–133, respectively. The E of the prepared CNT composites have been determined using Raman spectra and found to be in the range of 4.99-28.63 GPa, which are within the range of other reported CNT composites (∼1.5-95.40 GPa). The present work will help in the study of the measurement of mechanical properties of CNT based nanocomposites by nondestructive methods.