A 64-year-old man with lung cancer was given a laxative after his fourth cycle of platinum-etoposide chemotherapy, which caused profuse watery diarrhea. Subsequently, he developed progressive abdominal distension, nausea, vomiting, and hemodynamic instability. Laboratory tests showed severe metabolic acidosis, hyperlactatemia, and pancytopenia; imaging revealed massive intestinal fluid retention and elevated intra-abdominal pressure (IAP). Blood cultures confirmed ESBL-producing Escherichia coli bacteremia. In the ICU, he received mechanical ventilation, vasopressors, continuous renal replacement therapy, bowel decompression, and broad-spectrum antibiotics; IAP reached 28 mmHg, which meets criteria for abdominal compartment syndrome (ACS). Multidisciplinary treatment included hemodynamic optimization of PiCCO and targeted antimicrobial therapy. He was extubated on the 17th day and discharged from the ICU on the 19th. The case shows a rare occurrence of ACS after chemotherapy-induced mucositis complicated by septic shock and multiorgan failure.