Isolated left adrenal gland injuries following blunt abdominal trauma are extremely rare, accounting for only 1.5-4% of all adrenal trauma cases. Most traumatic injuries are right-sided and associated with other concurrent organ injuries. While acute, unilateral adrenal injuries can be asymptomatic, it is important to recognise the potentially life-threatening complications from haemorrhage and/or adrenal insufficiency. Due to its rarity, there are currently no established guidelines for management, monitoring, or follow-up of adrenal gland trauma. We present a case report of a rare, isolated, post-traumatic left adrenal gland haemorrhage. A 39-year-old man presented with mild abdominal pain following a mountain bike accident. Initial assessment revealed tenderness in the left upper quadrant with normal vital signs and biochemistry, but computer tomography (CT) imaging demonstrated an enlarged left adrenal gland with regional fat stranding and free fluid consistent with an acute adrenal haematoma. He was admitted to the ward for observation and discharged on day three of admission. At a six-week follow-up, he reported a complete resolution in symptoms. Follow-up CT of the adrenals at five months post-injury demonstrated complete resolution of the isolated adrenal haematoma. Post-traumatic isolated left adrenal gland injuries are rare in the reported literature, and this case highlights the lack of current guidelines for management and monitoring in cases of isolated adrenal haemorrhage. The current consensus appears to be appropriate with conservative management and follow-up with serial abdominal CT until the resolution of haemorrhage and/or symptoms.