Background: Anemia remains a major global health challenge, particularly in low- and middle-income countries. Medicinal plants rich in phytochemicals are widely used in traditional medicine for managing hematological disorders. However, systematic evidence on their hematopoietic effects remains limited. Methods: A systematic literature search was conducted across PubMed, Scopus, Web of Science, and Google Scholar for studies published up to December 2025. Experimental studies evaluating plant-derived phytochemicals on hematological parameters—hemoglobin (Hb), packed cell volume (PCV), red blood cells (RBC), and white blood cells (WBC) were included. Data extraction and risk of bias assessment were performed using the SYRCLE tool. A narrative synthesis was conducted, supported by quantitative summaries. Results: A total of 10 studies met the inclusion criteria, spanning Nigeria, India, China, Ghana, South Africa, and Brazil. Most studies utilized rodent models and evaluated aqueous, methanolic, and ethanolic plant extracts rich in flavonoids, alkaloids, saponins, and tannins. Phytochemical interventions consistently improved hematological indices. Hemoglobin levels increased by 0.6–4.3 g/dL, with corresponding increases in PCV and RBC counts, indicating enhanced erythropoiesis. WBC counts were also elevated, suggesting immunomodulatory effects. Substantial heterogeneity was observed (I² ≈ 89.8%). Conclusion: Phytochemical-rich medicinal plants exhibit significant hematopoietic and immunomodulatory effects. However, high heterogeneity and reliance on animal models highlight the need for well-designed clinical trials.