Research on the implications of negative emotions for creativity has yielded mixed findings. To clarify this relationship, we conducted a short‐term prospective study with data collected across two time points. We also explored the moderating roles of family expressiveness and gender in the creative process. The sample included 392 Japanese adolescents (54.7% female; age range: 12–13 years old). Adolescents reported on their experiences of negative activating emotion (e.g., fear, anxiety) and the degree to which their family members expressed positive emotions (e.g., expressing gratitude) toward each other. A drawing task and an alternative uses task (AUT) were used to measure adolescents' creativity. For creativity expressed in the drawing task, negative activating emotion enhanced creativity in girls only when their families' emotional expressivity was of low or average levels. For creativity indexed by the AUT, a high level of family expressiveness strengthened the relationship between negative activating emotion and creativity in boys but suppressed such a relationship in girls. Findings suggest that, at least among Japanese adolescents, the associations between negative activating emotions and creativity can depend on multiple factors, including family emotional expressivity, gender, and the nature of the creativity task.