This chapter explains the various ongoing demand of carbon nanotubes (CNTs) material for highly sensitive SPR sensors to detect chemical and gas molecules. It is broadly classified into six sections. The first section briefly describes the introduction, particularly the structure of the CNTs, different allotropes of carbon, synthesizes characterization of CNTs, various properties, and how it helps in the SPR-based sensor for greater response. The second section explains the famous growth method of the CNT layers. However, the optical properties of the CNT structure are presented in the third section. Sections 4 and 5 briefly describe its application in gas and chemical sensing and the advantages of CNT-based material over others. Finally, the last section summarizes the whole chapter, which concludes how the carbon-based material plays a vital role in the plasmonic-based sensor.