Premature return to play (RTP) following sports-related concussion (SRC) is associated with significant morbidity including risk of neurological and non-neurological injury, persistent post-concussion symptoms and chronic neurological deficits. Assessing athletes for RTP is critical but these decisions are currently based on clinical assessments that are subject to bias and symptomatic reporting that rely on compliance. An objective and easily obtained biomarker that can indicate recovery following SRC would aid clinicians to make safer RTP decisions. We performed a systematic review to identify potential biomarkers from saliva, urine and blood sources that could inform the clinical RTP decision. The MEDLINE database was searched. Inclusion criteria were studies focusing on adults diagnosed with SRC, fluid biomarkers from blood, saliva or urine and clinical recovery from SRC or at RTP. We assessed each biomarker for their time course post SRC and relationship to clinical recovery. Secondary outcomes included correlation with symptom scores and predictive value for prolonged RTP. We identified 8 studies all investigating blood-based markers of diffuse axonal injury (tau, NFL, SNTF), neuroglial injury (NSE, VLP-1, UCH-L1, S100B, GFAP), inflammation and hormonal disturbances. Tau, SNTF, UCH-1, GFAP, S100B and the inflammatory cytokine MCP-4 are raised post SRC and return to baseline by RTP. Changes in tau, NFL, SNTF, GFAP and MCP-4 post SRC correlate with severity of concussion as measured by symptom severity or RTP duration. There is only preliminary case-reporting for hormonal biomarkers. The evidence is limited by a lack of highly powered studies, variation in use of athletic and Contact sport controls (CSC) and a lack of consistent sampling and assessment protocols. There is promise for biomarkers to aid RTP decisions following SRC, most notably in use alongside clinical assessment in RTP criteria to allow greater precision in identifying mild and severe concussion.