Abstract Nostalgia is a prevalent emotion that confers psychological benefits and influences consumer behavior. We developed and validated the 98‐word Nostalgia Dictionary to automatize the assessment of nostalgicity in narratives (e.g., customer reviews, social media). First, we created an initial wordlist by identifying the most frequently used words in nostalgia narratives and by relying on the nostalgia literature. Second, we finalized the dictionary by testing experimentally the expanded wordlist for its capacity to differentiate nostalgia from related emotions. Third, we validated the dictionary by demonstrating that it corresponds to self‐reports and coder‐ratings of nostalgia, produces result patterns expected by theory, and predicts favorability ratings of books and consumer experiences, even after adjusting for positive emotion words. We discuss the potential of the Nostalgia Dictionary to advance research and practice.