Purpose: Renal Allograft Compartment Syndrome (RACS) is a rare but serious complication following renal transplant. In this report, we describe a case of this occurring in a paediatric patient and our key learning points. Methodology: A 4-year-old male with congenital nephrotic syndrome underwent a deceased donor kidney transplant. The day one post-operative ultrasound was unable to visualise the renal vein and demonstrated reverse diastolic flow in the renal artery, concerning for renal vein thrombosis. The patient was returned to theatre. The transplant kidney was found to be dusky, but when exposed from the surrounding space quickly became well perfused. The renal veins and arteries were patent. The kidney was repositioned intraperitoneally to allow adequate space. The patient recovered well initially. Unfortunately, in the coming months the graft exhibited poor function and a nephrectomy was undertaken. Results: This case highlights an important complication in the immediate post-operative period. RACS is rare, with an incidence of 1-2%. It is characterised by increased pressure in the iliac fossa site of the transplanted kidney, leading to reduction of blood supply to the graft. With non-specific clinical features, it is difficult to diagnose. Early diagnosis is integral, as recovery of the kidney can be possible with prompt surgical decompression. Despite quickly returning to theatre, the patient still developed eventual graft loss. Conclusion: RACS is a serious early complication that must be considered. Early diagnosis and prompt return to theatre are key to avoiding graft loss. Doppler ultrasound is also a pivotal tool in assessment.