This study introduces a rapid, cost-effective, and efficient method for in ovo xenografting of patient-derived acute lymphoblastic leukemia (ALL) cells, encompassing both B-cell and T-cell lineages. Using fertilized chicken embryos, we injected patient-derived B-ALL and T-ALL cells into the vasculature of embryos 11 days post-fertilization (11dpf). Remarkably, four days following the injection, the engrafted human leukemia cells exhibited significant survival, proliferation, and vascular colonization within the developing chicken embryo. By 15dpf, we detected a notable increase in CD10/CD19+ B-ALL and CD4/CD8+ T-ALL cells in blood samples from the embryo's vasculature, confirming successful engraftment. This system facilitates efficient and reproducible assessment of leukemia cell behavior in a living organism without the considerable costs and ethical constraints associated with other animal models. This rapid approach provides a high-throughput and biologically relevant in vivo platform for evaluating potential therapeutic compounds. The in ovo patient-derived xenograft (PDX)-ALL system presented here offers a promising tool for preclinical drug screening, mechanistic studies, and potentially for personalized medicine approaches in leukemia research.