Surgical site infections (SSI) cause substantial morbidity and pose a burden to acute healthcare services after surgery. We aimed to investigate whether a smartphone-delivered wound assessment tool can expedite diagnosis and treatment of SSI after emergency abdominal surgery. This single-blinded randomised control trial (NCT02704897) enrolled adult emergency abdominal surgery patients in two tertiary care hospitals. Patients were randomised (1:1) to routine postoperative care or additional access to a smartphone-delivered wound assessment tool for 30-days postoperatively. Patient-reported SSI symptoms and wound photographs were requested on postoperative days 3, 7, and 15. The primary outcome was time-to-diagnosis of SSI (Centers for Disease Control definition). 492 patients were randomised (smartphone intervention: 223; routine care: 269). There was no significant difference in the 30-day SSI rate between trial arms: 21 (9.4%) in smartphone vs 20 (7.4%, p=0.513) in routine care. Among the smartphone group, 32.3% (n=72) did not utilise the tool. There was no significant difference in time-to-diagnosis of SSI for patients receiving the intervention (-2.5 days, 95% CI: -6.61.6, p=0.225). However, patients in the smartphone group had 3.7-times higher odds of diagnosis within 7 postoperative days (95% CI: 1.0213.51, p=0.043). The smartphone group had significantly reduced community care attendance (OR: 0.57, 95% CI: 0.340.94, p=0.030), similar hospital attendance (OR: 0.76, 95% CI: 0.281.96, p=0.577), and significantly better experiences in accessing care (OR: 2.02, 95% CI: 1.173.53, p=0.013). Smartphone-delivered wound follow-up is feasible following emergency abdominal surgery. This can facilitate triage to the appropriate level of assessment required, allowing earlier postoperative diagnosis of SSI.