The World Health Organization Surgical Safety Checklist (SSC), now used by healthcare providers worldwide, has proved to be useful in the improvement of patients' health through the reduction of mortality and morbidity after surgery. In the Emilia-Romagna region in Italy the SSC is accompanied by a document that registers any non-conformity (NC) identified during SSC completion. This study aimed to investigate the association between surgical complications and checklist compliance, in terms of incompleteness and presence of NCs, using data from the Modena Local Health Unit (LHU). We used data from surgeries performed in the Modena LHU between 2018 and 2022, with their SSC and related NC document. We estimated relative risks (RRs) of complications fitting three modified Poisson regression models. Model 1 included checklist incompleteness and NC presence, Model 2 adjusted Model 1 for patients' sex and age group, and Model 3 adjusted Model 2 for the other potential confounders. We also performed a sensitivity analysis estimating the same three models including death outcomes as complications. We found an increased risk of complications for both checklist incompleteness (unadjusted RR [uRR]= 2.04; 95% confidence interval [CI]: 1.17 to 3.54) and presence of NCs (uRR = 2.35; 95% CI: 1.71 to 3.22). Results were consistent after adjustment and in the sensitivity analysis. Improving checklist compliance can reduce the risk of surgical complications. In particular, NCs are a risk factor that must be further investigated to better understand their relationship with complications. We believe that NCs data recording is helpful for both researchers in the scope of surgical complications, and healthcare professionals in the operating room.