This review examines the current literature to identify biomarkers of frailty across patients with solid tumors. We conducted the systematic review using preferred reporting items for systematic reviews and meta-analysis guidelines (PRISMA). PubMed, Web of Science, and Embase databases were searched from their inception to December 08, 2021, for reports of biomarkers and frailty. Two reviewers independently screened titles, abstracts, and full-text articles. A quality assessment was conducted using NHLBI Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies, and Quality Assessment of Case-Control Studies. In total, 915 reports were screened, and 14 full-text articles were included in the review. Most studies included breast tumors, were cross-sectional in design, and measured biomarkers at baseline or pre-treatment. Frailty tools varied with Fried Frailty Phenotype and the geriatric assessment most frequently used. Increased inflammatory parameters (i.e., Interleukin-6, Neutrophil Lymphocyte Ratio, Glasgow Prognostic Score-2) were associated with frailty severity. Only six studies were rated as good quality using assessment ratings. Together, the small number of studies and heterogeneity in frailty assessment limited our ability to draw conclusions from the extant literature. Future research is needed to identify potential target biomarkers of frailty in cancer survivors that may aid in early detection and referral.