Background: Urgent-start peritoneal dialysis (UPD) has emerged as an alternative modality for initiating kidney replacement therapy when immediate hemodialysis is not available. However, early initiation after catheter placement may increase the risk of mechanical complications. Evidence from real-world settings, particularly in resource-limited healthcare systems, remains limited. Objective: To determine the frequency of early complications associated with urgent-start peritoneal dialysis and to identify clinical factors associated with their occurrence. Methods: We conducted a prospective observational cohort study including adult patients with chronic kidney disease who initiated peritoneal dialysis within 14 days after catheter placement at a public hospital in Mexico. Patients were followed for 30 days after dialysis initiation. The primary outcome was the occurrence of any dialysis-related complication within 30 days after initiation of peritoneal dialysis. Comparisons were performed according to dialysis initiation timing (<72 h vs. ≥72 h). Multivariable logistic regression was used to identify independent predictors of complications. Results: Sixty-five patients were included, of whom 29 (44.6%) developed complications within the first 30 days. Mechanical complications predominated, particularly pericatheter leakage (18.5%) and drainage failure (10.8%). Patients who initiated dialysis within 72 h after catheter placement experienced a significantly higher complication rate. In multivariable analysis, initiation of peritoneal dialysis within <72 h remained independently associated with complications (OR 5.75, 95% CI 1.06–31.29, p = 0.043). Conclusions: Initiating peritoneal dialysis within 72 h after catheter placement was associated with a significantly increased risk of early complications. When clinically feasible, delaying dialysis initiation beyond 72 h may reduce mechanical complications in urgent-start peritoneal dialysis programs.