Carbon nanotubes (CNTs) were produced from two plastic waste feedstocks, a polypropylene (PP)-dominated mask and a solid recovered fuel (SRF) with a high content of non-recyclable mixed plastics, using a pyrolysis-chemical vapor deposition (CVD) process. FeMo/MgO and CoMo/MgO catalysts were used for CNT growth using pyrolysis gases containing various hydrocarbons. It was found that CoMo/MgO produced selective and small-walled CNTs, while FeMo/MgO produced high-yield multi-walled CNTs. The CNTs produced from the mask feedstock exhibited higher yield, diameter, and purity compared to those produced from the SRF feedstock. The resulting CNTs were tested as conductive additives in the cathode of a lithium-ion battery (LIB). Electrochemical measurements demonstrated that CNTs produced with FeMo/MgO outperformed commercially available carbon black. This study presents a novel approach for plastic waste utilization, where CNTs produced from plastic waste can be utilized as effective conductive additives for LIB cathodes.