Purpose: This systematic review and meta-analysis aims to analyze the risk of prosthesis complications across different implant diameters. Materials and Methods: An electronic search across PubMed (MEDLINE), Embase, Scopus, and Cochrane Central Register of Controlled Trials until December 2023 was performed. Studies comparing implant prosthesis complications among extra-narrow (<3.0 mm), narrow (≥3.0 to <3.75 mm), standard (≥3.75 to <5 mm), and wide-diameter (≥5 mm) implants were included. Meta-analyses were performed to evaluate the risk ratio of prosthesis complications across different diameters, particularly in non-full arch implant-supported fixed dental prostheses (ISFDP). Results: Eighteen clinical studies were included. In non-full arch ISFDP, the most prevalent complication was screw loosening in narrow, standard, and wide-diameter implants (17.28%, 4.08% and 12.45%, respectively), and decementation (3.4%) in extra-narrow diameter implants. In implant overdentures, extra-narrow, narrow and standard-diameter implants demonstrated high rates of retentive cap wear (58.33%, 80.49% and 70%, respectively), whereas wide-diameter implants had 16.67% overdenture repair. The meta-analyses showed a risk ratio of 0.20 (95% confidence interval= 0.04 to 0.94, p= 0.04) and 0.17 (95% CI= 0.06 to 0.45, p< 0.0004) for abutment fracture in single crowns and ISFDP comparing narrow versus standard-diameter implants. No significant differences in risk ratios were observed for screw loosening, decementation, porcelain chipping, fracture, or screw fracture among the different diameter groups. Conclusions: This systematic review highlights that screw loosening and retentive cap wear are the most common prosthesis complications in ISFDP and overdentures, regardless of implant diameter. While narrow-diameter implants have a lower risk of abutment fracture compared to standard-diameter implants, clinicians should carefully consider patient characteristics, implant locations, and abutment features when selecting the ideal implant diameter.