The use of polymers and their composites in the aerospace and automobile industry has increased over the past few decades. Utilizing polymers over metals has many advantages, including reducing weight, improving fuel efficiency, and enhancing corrosion resistance. However, when using polymers, heat dissipation becomes a critical factor as overheating can result in premature failure of devices. To address this issue, various thermally conductive materials, such as carbon fibres, can be used as fillers to increase the thermal conductivity (TC) of polymers. Along with it, additive manufacturing can provide an extra edge in improving the heat dissipation of complex structures. This research focuses on enhancing the TC of carbon fibre-filled polyetherimide (PEI-CF) filament by optimizing its 3D printing process parameters. We investigate the influence of printing temperature on the resulting porosity and TC. Moreover, we study the effect of moisture content on the TC of 3D-printed objects made from PEI-CF. Through a systematic characterization and analysis, we establish a set of optimized printing conditions to maximize TC. The results demonstrate a significant improvement in thermal performance, showcasing the potential for utilizing 3D-printed PEI-CF in heat dissipation applications.