Introduction <p>Obesity is a growing public health priority leading to significant morbidity, mortality, and growing interest in medical and surgical interventions. Due to their perceived long-term efficacy, surgical interventions have gained popularity over the past few decades, supported by recent technical advances. Globally, laparoscopic sleeve gastrectomy (LSG) is the most frequently performed bariatric surgery. Although generally safe, potential post-operative complications include leakage and intra-abdominal infections. Splenic abscesses post-LSG are rare, with only a few cases reported, amongst which <i>Prevotella nigrescens</i> was not previously isolated. We describe the rare occurrence of <i>Prevotella nigrescens</i> splenic abscess and bacteraemia following LSG.</p> Case presentation <p>A 31-year-old female presented three weeks after LSG with fever, rigors, vomiting, and abdominal and shoulder pains. Abdominal ultrasound showed a heterogeneous hypoechoic structure in the superior splenorenal region, and a computed tomography scan reported a 5&#xa0;cm hypodense septated lesion with subtle peripheral irregular enhancement in the superomedial spleen. A chest x-ray identified a left-sided pleural effusion. Upon CT-guided splenic abscess aspiration, pus was obtained and processed for microbiological evaluation. Eventually, both pus and blood and cultures grew <i>Prevotella nigrescens.</i> The patient was treated with antimicrobials and percutaneous aspiration, leading to safe outcomes.</p> Conclusion <p>Splenic abscesses are a rare complication of LSG. Patients usually present with febrile symptoms and abdominal pains best evaluated radiologically by CT scans, followed by pathogen identification, guiding safe management approaches. Parenteral antibiotics and source control by percutaneous aspiration are a mainstay of management.</p> Clinical trial number <p>Not applicable.</p>