Throughout history, collectivism has contributed much to social bonding and human wellness. However, it remains unclear whether the collectivism-wellness equation still applies, when there is a mismatch between the collectivistic values and the ecological environment of urbanisation. Testing the hypothesis of cultural value mismatch (e.g., high urbanised & high collectivistic, or low urbanised & low collectivistic), two studies were designed to examine the relationship between collectivism and emotional wellbeing in China, with urbanisation as moderator. Based on the emotion analysis of tweets among 1.6 millions of Weibo users, Study 1 found that the province-level collectivism scores were significantly and positively related to negative emotions in high urbanised provinces, but this relationship was not significant in low or middle urbanised provinces. Using a nationwide survey dataset, Study 2 showed that, on the individual level, those with higher collectivism reported less negative emotions, but only in low- and middle-urbanised provinces, not in high-urbanised provinces. On positive emotions in all areas, the positive effect of collectivism was observed on individual level, but not on province level. These findings support the value mismatch hypothesis of urbanisation, suggesting that the purchasing power of collectivism on wellbeing is compromised in urbanising China.