Metallic substrates and polymer adhesive in composite-metal joints have a relatively large coefficient of thermal expansion (CTE) mismatch, which is a barrier in the growing market of electric vehicles and their battery structures. It is reported that adding carbon nanotubes (CNTs) to the adhesive reduces the CTE of the CNT-enhanced polymer adhesive multi-material system, and therefore when used in adhesively bonded joints it would, theoretically, result in low CTE mismatch in the joint system. The current article presents the influence of two specific mass ratios of CNTs on the CTE of the enhanced polymer. It was observed that the addition of 1.0 wt\% and 2.68 wt\% of multi-walled CNTs (MWCNTs) decreased the CTE of the polymer adhesive from 7.5 × 10−5◦ C−1 (pristine level) to 5.87 × 10−5◦ C−1 and 4.43 × 10−5◦ C−1, respectively, by 22\% and 41\% reductions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.