The recovery of nitrogen and phosphorus from anaerobic digestate through struvite crystallization is a sustainable approach for nutrient recycling. However, the effects of hydraulic retention time (HRT) and substrate mixing ratios on struvite recovery from the solid fraction of anaerobic digestate remain insufficiently understood. This study investigated struvite (MgNH₄PO₄.6H₂O) crystallization as a nutrient recovery strategy from the solid fraction of anaerobic digestate derived from co-digestion of chicken droppings (CD) and food waste (FW) across three hydraulic retention times (15, 30, and 60 days) and six substrate treatment ratios. Solid-liquid separation of the digestate was done by centrifugation at 2500 rpm for 15 minutes. Solid digestate fractions were characterized and subjected to acid hydrolysis until the pH was 2. Struvite precipitation was conducted at pH 9.0 with a supplementary of 1 M MgCl₂ and 1 M KH₂PO₄ in a ratio of 3:2.5 (Mg:P). Recovery efficiencies of both nitrogen (NH₄-N) and phosphorus (PO₄-P) increased significantly with the increase in hydraulic retention time, with the highest values recorded at 60 days in treatment T3 (70% food waste:30% chicken droppings). The maximum recovery efficiencies of nitrogen and phosphorus were 94.4% and 72.8%, respectively. Further, struvite production rates were in the range of 8.31–10.80 g/50 mL acid extract digestate. The study suggests using T3 (70% food waste and 30% chicken droppings) for practical implementation over a 60-day digestion period, demonstrating the viability of the digestates. The use of this method in anaerobic digestion contributes to the principles of the circular economy and sustainable nutrient management.