Tethered cord syndrome is associated with motor and sensory deficits. Our objective was to summarize evidence regarding the diagnosis, prophylactic surgery, symptomatic treatment, and repeat surgery of tethered spinal cord in a systematic review (CRD42023461296). We searched 13 databases, reference-mined reviews, and contacted authors to identify diagnostic accuracy studies and treatment studies published until March 2024. One reviewer abstracted data, and a content expert checked the data for accuracy. We assessed the risk of bias, strength of evidence (SoE), and applicability. The evidence base includes 103 controlled studies, many with risk of bias and applicability concerns, and 355 case series providing additional clinical information. We found moderate SoE for MRI diagnosing tethered spinal cord, with medium to high diagnostic sensitivity and specificity. A small number of prophylactic surgery studies suggested motor function benefits and stability of neurologic status over time, but also complications such as surgical site infection (low SoE). A larger body of evidence documents treatments for symptomatic patients; studies revealed improvement in neurologic status after surgical detethering (low SoE), but also postoperative complications such as cerebrospinal fluid leakage (moderate SoE). A small body of evidence exists for retethering treatment (low or insufficient SoE for all outcomes). There was insufficient evidence for key outcomes (eg, over- or undertreatment, clinical impact of diagnostic modalities, ambulation, quality of life). This comprehensive overview informs difficult clinical decisions that parents and their children with tethered spinal cords, as well as their health care providers, face.