High-grade serous ovarian carcinoma (HGOC) is frequently diagnosed at an advanced stage, leading to high recurrence rates. This case report highlights the utility of [68Ga]Ga-FAPI-46 PET/MRI in detecting previously unidentified lymph node metastases in a 75-year-old woman with recurrent HGOC, which altered the treatment strategy. The imaging revealed increased [68Ga]Ga-FAPI-46 uptake in nonenlarged mediastinal and left perihilar lymph nodes, reclassifying the patient from FIGO IIIb to FIGO stage IV and prompting a change in therapeutic management.