The number of single-child families has been increasing across developing countries during the last decades. We aimed to examine the association between being a single child (SC) and subjective health complaints (SHCs) in Iranian children and adolescents. This study was conducted as a part of the fifth survey of a national surveillance program entitled Childhood and Adolescence Surveillance and Prevention of Adult Non-communicable disease (CASPIAN-V). This national survey included a total of 14,400 students 7-18 years and their parents from rural and urban areas in 30 provinces of Iran. Data on demographic characteristics, lifestyle variables, and SHCs were measured using the questionnaire of the World Health Organization on Global School-based Health Survey (WHO-GSHS). Multivariate logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (95%CI) for the association of being an SC with SHCs. Data on 14,151 participants were available for this study, of whom 7.7% (1092) were SCs. The most frequent SHCs were irritability (37.1%, 95%CI: 36.3-37.9%), feeling nervous 32.5%, 95% CI: (31.7-33.3%), and headache 24.3%, 95%CI: (23.6-25.0% ). In the multivariate model, being an SC significantly increased the odds of dizziness [adjusted OR (95% CI): 1.37(1.08-1.72)] and backache complaint [1.22(1.01-1.47)]. The association of being an SC with other SHCs (feeling low, irritability, feeling nervous, difficulty in getting to sleep, headache, stomachache) was not statistically significant (p value > 0.05). Our results suggest that being an SC may be associated with higher odds of dizziness and backache complaints.