Joffrey dies in Game of Thrones Season 4, Episode 2, titled “The Lion and the Rose.” He chokes on his wine at his wedding feast and dies in the arms of his mother, Cersei, with Tyrion’s unwitting presence at the heart of the moment. The poisoning is later revealed to have been orchestrated by Olenna Tyrell (with covert assistance from others) to remove Joffrey from the throne. If you’d like, I can add a quick recap of the key clues and who’s implicated in this murder mystery across the subsequent episodes.