Objective: This systematic review evaluates all published studies comparing biologic and synthetic meshes in implant-based breast reconstruction (IBBR), to determine which category of mesh produces the most favorable outcomes. Summary Background Data: Breast cancer is the most common cancer in women globally. Implant-based breast reconstruction is currently the most popular method of postmastectomy reconstruction, and recently, the use of surgical mesh in IBBR has become commonplace. Although there is a long-standing belief among surgeons that biologic mesh is superior to synthetic mesh in terms of surgical complications and patient outcomes, few studies exist to support this claim. Methods: A systematic search of the EMBASE, PubMed, and Cochrane databases was performed in January 2022. Primary literature studies comparing biologic and synthetic meshes within the same experimental framework were included. Study quality and bias were assessed using the validated Methodological Index for Non-Randomized Studies criteria. Results: After duplicate removal, 109 publications were reviewed, with 12 meeting the predetermined inclusion criteria. Outcomes included common surgical complications, histological analysis, interactions with oncologic therapies, quality of life measures, and esthetic outcomes. Across all 12 studies, synthetic meshes were rated as at least equivalent to biologic meshes for every reported outcome. On average, the studies in this review tended to have moderate Methodological Index for Non-Randomized Studies scores. Conclusion: This systematic review offers the first comprehensive evaluation of all publications comparing biologic and synthetic meshes in IBBR. The consistent finding that synthetic meshes are at least equivalent to biologic meshes across a range of clinical outcomes offers a compelling argument in favor of prioritizing the use of synthetic meshes in IBBR.