This experiment tests how mouse and fish spleen cell proliferation are affected by different concentrations of CBD oil. Spleen cell proliferation assay was conducted in the presence of concanavalin A and lipopolysaccharide mitogens for both mouse and fish spleen cells. Results indicate that for mouse spleen T cells, 11.49 µg/mL of CBD was effective in increasing the T cell proliferation when the cells were simulated by Con A. For mouse B cells, CBD seems to have had an inhibitory effect on the cells by reducing the proliferation caused by the mitogen. Similar results are seen in the case of fish spleen cells stimulated with LPS, where the inhibition of spleen cells is seen at the final CBD concentration of 0.46 µg/mL. From our current research, CBD may have different effects based on the species, whether they need to enhance their immune response or reduce inflammation to be healthy. It also seems to have different effect on different parts of the immune system. By administering the proper dosage of CBD on a case by case basis, health benefits can be achieved.