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Methaemoglobinemia is a rarely encountered haematological condition that can be congenital or acquired. Methaemoglobin is an abnormal type of haemoglobin that is oxidised and incapable of delivering oxygen to tissues. This can lead to cyanosis, hypoxia, acidosis, arrhythmias, and more, depending on the methaemoglobin concentration, and can be fatal. A thorough understanding of the disease process is essential to develop a suitable anaesthesia plan and prevent complications. Ensuring adequate tissue oxygenation, assessing oxygenation using appropriate monitoring tools, and avoiding trigger agents are the cornerstones of anaesthetic management. A co-oximeter is the gold standard for monitoring, as it detects and quantifies methaemoglobin levels. Methylene blue acts as an antidote, functioning as an oxidising agent that converts itself to leukomethylene blue, which reduces methaemoglobin back to haemoglobin. In the present case of a 60-year-old male, the authors present the anaesthetic management and challenges in a diagnosed case of congenital methaemoglobinemia undergoing laparoscopic inguinal hernia repair surgery. Methylene blue was administered prophylactically preoperatively. An arterial line was established before anaesthesia induction for close haemodynamic monitoring and quick blood gas and oxyhaemoglobin sampling, as a co-oximeter was not available. Adequate oxygenation during induction and emergence was ensured to prevent hypoxia, given the lower amount of normal haemoglobin in these patients. All potential trigger agents, such as nitrous oxide, local anaesthetics, nitrates, and metoclopramide, were avoided. The patient had an uneventful intraoperative and postoperative course and was discharged after one day.