This study aimed to investigate the histological growth and Myoz1 gene expression and evaluated the level of glycogen in the iliofibularis muscle of broiler chickens at 2, 4, and 5 weeks of age. By investigating the structural changes in muscle fibers and the corresponding alterations in Myoz1 gene levels, this research sought to elucidate the relationship between age, muscle growth, and gene expression in the iliofibularis muscle group. Understanding these developmental processes is crucial for optimizing broiler production and potentially providing insights into muscle growth and development in other species.  In this study, fifteen broiler chickens were examined to investigate the histological structure and evaluate the level of the Myoz1 gene in the iliofibularis muscles at three different ages: 2 weeks, 4 weeks, and 5 weeks. The muscle fibers are cylindrical and multinucleated, with elongated nuclei beneath the sarcolemma. The muscle fibers are surrounded by a very thin layer of endomysium, which is composed of fibroelastic connective tissue. Each fascicle of muscle fibers is surrounded by a dense, irregular connective tissue called the perimysium. A cluster of muscle fascicles is surrounded by a layer of dense, irregular connective tissue called the epimysium. The size and organization of muscle fibers increase with age. At 5 weeks, the muscle fibers become larger and more uniform. The mean areas of muscle fibers at 2 weeks, 4 weeks, and 5 weeks were 233.1± 0.0099, 492.32± 0.0079, and 1177.56± 0.0098 µm2, respectively. Our results show the muscle fibers in the third group had a highly significant difference from the muscle fibers of the iliofibularis muscle in the first and second groups. The highest average expression was found in the third group (5 weeks old), while the lowest was in the first group (2 weeks old). Our findings indicate statistical analysis confirmed iliofibularis muscle in the third group had a highly significant difference with iliofibularis muscle in the first and second groups (Ƿ=0.0000269) and (Ƿ=0.000025), respectively. Overall, the findings suggested an age-dependent rise in myzo1 gene expression within the iliofibularis muscle in the third group of broiler chickens.