Who is happier in solitude? Solitude, defined as the objective state of being alone without online or offline social interactions, is a common daily experience whose affective consequences vary across age. Previous studies have shown that personality moderates these age differences without considering personality as culture-specific. Because personality structures and their social meanings vary across cultures, it remains unclear whether the interaction between personality and culture accounts for age differences in solitude experiences. This study investigated the moderating effects of personality and culture on age differences in the solitude-affect association, using the Chinese Personality Assessment Inventory (CPAI) to capture culture-specific effects of personality traits. In CPAI, dimensions of Traditionalism vs. Modernity, Ren Qing, Social Sensitivity, Discipline, Harmony, and Thrift vs. Extravagance were analysed as moderators. Five hundred participants (the UK: N = 235, Mage = 44.57, SDage = 16.74, 57.45% women; HK: N = 265, Mage = 45.95, SDage = 17.66, 66.04% women; age range = 19-93) completed a seven-day smartphone-based experience sampling assessment (total N = 16,187). Momentary solitude, positive affect (PA), and negative affect (NA) were reported five times per day. We found that culture, age, and CPAI dimensions moderated the association between solitude and affective experiences. Distinct interaction patterns emerged across culture and age groups. For younger adults in the UK, a higher level of traditionalism weakened the negative link between solitude and PA and the positive link between solitude and NA. For younger adults in HK, higher levels of traditionalism, Ren Qing, social sensitivity, and harmony strengthened the positive link between solitude and NA. For older adults in HK, higher levels of Ren Qing, social sensitivity, and harmony weakened the positive link between solitude and NA. These results highlighted the significance of incorporating cultural contexts to better understand how personalities shape age-related differences in solitude experiences.