Marine debris ingestion and entanglement have caused morbidity and mortality in multiple marine species, including all seven species of sea turtles. This case series outlines six cases in which advanced imaging modalities were used to diagnose marine debris–induced foreign body obstructions and to aid in the treatment of wounds caused by marine debris entanglement. Prefemoral ultrasonography was used to correctly diagnose a monofilament fishing line linear foreign body obstruction in a juvenile female Kemp's Ridley sea turtle (Lepidochelys kempii) and a subadult female loggerhead sea turtle (Caretta caretta). Administration of iodinated contrast confirmed a complete upper gastrointestinal obstruction in a juvenile green sea turtle (Chelonia mydas). Traditional radiographs were nondiagnostic in all three animals. Barium-impregnated polyethylene spheres were used to identify a partial gastrointestinal foreign body obstruction in a juvenile green sea turtle. Endoscopy was used in multiple cases as both a diagnostic and a therapeutic tool. This case series demonstrates that contrast radiography, ultrasonography, and endoscopy are accurate diagnostic tools for the identification of marine debris–induced foreign body obstructions in sea turtles.