Background and Objectives: Thyroxine is important for brain development. Improper hypothyroid treatment may lead to cognitive and motor impairment, thereby affecting the quality of life. We analyzed the correlation between age at first treatment, length of treatment, initial levothyroxine (LT4) dose, and serum levels of free thyroxine (fT4) and thyroid stimulating hormone (TSH) and pediatric quality of life in patients with congenital hypothyroidism (CH). Materials and Methods: This research was a cross-sectional study of 41 children with CH who consumed LT4 for at least 3 months during March 2019-December 2019. The quality of life was assessed from parents’ reports using the Pediatric Quality of Life Inventory (PedsQL) generic scale. Spearman correlation analysis was carried out, and statistical significance was set at p＜0.05. Results: A total of 17 of the 41 children were girls. The mean PedsQL scores in physical and psychosocial functioning were 78.12 (68.75-100) and 233.30 (215-251.67), respectively. Age at first treatment was correlated with physical functioning (r=−0.501, p＜0.05) and psychosocial functioning (r=−0.440, p＜0.05). The initial LT4 dose was negatively correlated with physical functioning (r=−0.568, p＜0.05) and psychosocial functioning (r=−0.482, p＜0.05). The length of treatment showed a positive correlation with physical functioning (r=0.776, p＜0.05) and psychosocial functioning (r= −0.852, p＜0.05). However, the serum fT4 and TSH levels were not correlated with quality of life in children with CH (p＞0.05). Conclusion Age at first treatment, initial dose of LT4, and length of treatment were correlated with quality of life in children with CH.