This study evaluates the impact of composting on the circularity of a poultry system in Mexico, specifically at the farm Avícolas Campesinos Bondojito (ACB), located in Huichapan, Hidalgo. A systems thinking approach was used to analyze the technological, social, and economic components of the poultry system and to characterize its by-products, such as poultry manure, based on their physicochemical properties and viability as biofertilizers. The composting process was experimentally evaluated by monitoring temperature, pH, and electrical conductivity (EC) at the pilot scale. The agro-inputs produced were analyzed to assess their quality as biofertilizers. Additionally, the Nested Circularity Framework was applied to evaluate the impact of composting on biomass production, energy efficiency, and nutrient recycling under two waste management scenarios. The results identified poultry manure as the primary by-product of the system, with 74.6 Mg per cycle and a composition of 36.7%_C, 3.27%_N, 1.51%_P, and 2.9%_K; a pH of 7.62; an EC of 1062 µS·cm^-1; and a C:N ratio of 11.34:1, which limited its use as direct fertilizer due to instability. Composting improved its viability as an agro-input by increasing the C:N ratio (to 31.84) through mixing it with carbon-rich materials, which enhanced the thermal evolution, sanitization, and nutrient availability, particularly that of nitrogen (from 102.3 to 258.2 ppm of N). Ultimately, integrating poultry manure composting and an agricultural subsystem within the poultry production system could significantly enhance the farm’s circularity. This would include better biomass utilization (the additional production of 7.72 Mg of oat grain and 9.6 Mg of straw), reduced reliance on external inputs (straw for bedding), and increased energy efficiency (56% vs 44%). These strategies suggest composting optimizes waste management and contributes to a more sustainable and efficient production system.