Studies of emotion vocabulary and understanding typically focus on early childhood. Yet, emotion abilities continue to develop into adolescence, making it an important and underinvestigated area of research. This study presents evidence that adolescents’ emotion vocabulary undergoes active development, becomes more broad and sophisticated, varies by gender, and is not captured adequately by recognition-based approaches. Adolescents were asked to generate emotion words for five emotion categories—happy, relaxed, angry, sad, and nervous. Responses included emotion words (e.g., joyous) and nonemotion terms such as metaphors (e.g., boiling), social experiences (e.g., underappreciated), and personality traits (e.g., shy). Girls generated significantly more responses than boys. Older adolescents generated significantly more emotion words (e.g., describing someone who is happy as joyful, exuberant or ecstatic), while younger adolescents produced more nonemotion responses (e.g., describing someone who is happy as smiley, friendly, or full of life). Students’ grade, total number of responses they produced, and performance on the recognition test of emotion understanding predicted their emotion vocabulary.