There has been literature on the relationship of food and happiness, but the role of second-hand smoking is less understood. Therefore, the aim of the present study was to examine if second-hand smoking might mediate the associations of food consumption and subjective happiness in a country-wide and population-based setting. Data was retrieved from the Scottish Health Survey, 2012. Information on demographics, frequency of consuming certain foods and subjective happiness was obtained by household interview. Chi-square test and survey-weighted logistic regression modelling were performed. Of the included Scottish adults aged 16–99 (n = 4815), 15.4 % (n = 677) reported that they were unhappy. It was observed that eating lots of potatoes, some meat, some oily fish and some pastries were inversely associated with unhappiness. People who consumed vegetables and fruits on the day before the health interview were also found to be less unhappy, compared to their counterparts. However, the protective effect from fruits disappeared after additionally adjusting for indoor second-hand smoking while the protective effects from other foods mentioned above have also been lessened. In addition, cumulatively people who consumed more “happy foods” (mentioned above) were more likely to report subjective happiness, compared to those who did not consume any of those. For future research, longitudinally monitoring on the associations among food, household environment and psychological well-being and both the short-term and long-term effects would be suggested. For policy implications, Removal of indoor second-hand smoking to retain the protective effects from happy foods on well-being should be encouraged.