Studies show that loneliness was higher during the pandemic than in the pre-pandemic periods, with negative consequences on individual happiness. This study extends current knowledge by investigating the indirect effects of somatic symptoms and psychological distress in the loneliness-happiness relationship during the COVID-19 lockdown. The cross-sectional sample comprises 538 Nigerian adults (Meanage = 36.48 ± 12.03) with 43% females. Data were collected using structured self-report instruments and subjected to path analyses in SPSS AMOS. Results showed that loneliness and happiness were negatively related. Loneliness and happiness were indirectly related through the successive association between somatic symptoms and psychological distress. Specifically, greater loneliness was associated with increased somatic symptoms, which in turn were associated with greater psychological distress and reduced happiness levels. Clinicians can manage the decline in happiness from loneliness during the pandemic lockdown by administering treatments that mitigate somatic symptoms and psychological distress in concerned clients.