Additive manufacturing (AM), shows promising advancements in layer-based modeling displaying its potential for substantial waste reduction. Out of all the AM methods, the most cost-effective and popular choice for prototyping and making customized parts is fused deposition modeling (FDM). This research investigates how various FDM process parameters specifically layer thickness, raster angle, and printing speed affect the mechanical properties of 3D-printed PETG (polyethylene terephthalate glycol) specimens reinforced with carbon fiber (CF). Optimal settings, including a 0° raster angle, 0.2 mm layer thickness, and 40 mm/s printing speed, enhance both tensile and flexural strength due to improvement in material bonding and alignment. Interestingly, lower values for raster angle, layer thickness, and printing speed also lead to notable improvements in mechanical properties. Contour and interaction plots provide valuable insights into the significant impact of these parameters. The study also explores how different printing speeds influence the mechanical characteristics of CF-reinforced PETG specimens. Furthermore, the comparative analysis demonstrated that incorporating carbon fiber into recycled PET waste materials resulted in an approximately 30% increase in tensile strength. These findings imply that using CF with plastic waste in large-scale industries can pave the way for innovative solutions, enhancing performance and sustainability, especially in the automotive, and defence sectors.