Monitoring surgical wounds post-operatively is necessary to prevent infection, dehiscence and other complications. However, the monitoring of deep surgical sites is typically limited to indirect observations or to costly radiological investigations that often fail to detect complications before they become severe. Bioelectronic sensors could provide accurate and continuous monitoring from within the body, but the form factors of existing devices are not amenable to integration with sensitive wound tissues and to wireless data transmission. Here we show that multifilament surgical sutures functionalized with a conductive polymer and incorporating pledgets with capacitive sensors operated via radiofrequency identification can be used to monitor physicochemical states of deep surgical sites. We show in live pigs that the sutures can monitor wound integrity, gastric leakage and tissue micromotions, and in rodents that the healing outcomes are equivalent to those of medical-grade sutures. Battery-free wirelessly operated bioelectronic sutures may facilitate post-surgical monitoring in a wide range of interventions.