This paper delineates cultural tightness into formal versus informal aspects to depict the strength of norms and the extent of sanctions emanating from both formal and informal norms. Organizations with high formal cultural tightness regulate behaviors through explicit written norms and official sanctions, whereas those with high informal cultural tightness regulate behaviors through uncodified norms, collective beliefs, and informal social sanctions. Through a field study across 14 diverse companies in two countries (Malaysia and the Philippines) and two experiments involving participants from the United States, we found that perceived informal cultural tightness consistently exerts a more significant impact on stifling employee creativity than perceived formal cultural tightness. Additionally, we discovered that these two aspects of cultural tightness also potentially interact to influence employee creativity. Lastly, we identified promotion-focused (but not prevention-focused) self-regulation as a likely mechanism through which informal cultural tightness affects employee creativity. These findings contribute to cultural tightness-looseness theory and research on how organizational culture affects employee creativity.