Background: The wide biodiversity of marine animals provides a rich source of potential bioactive materials with biomedical applications. Aim: This study aimed to test the in vitro and in vivo anti-tumor effects of the purple fluid and egg extracts from Aplysia fasciata inhabiting the Egyptian marine water. Methods: The cytotoxicity of both the purple fluid and egg extracts were analysed in vitro against Ehrlich ascites carcinoma (EAC) cells by the trypan blue exclusion, MTT reduction assay and flow cytometry. The anti-EAC immunological effects of both extracts were assessed by blood counting and flow cytometry in mice challenged with EAC cells.  Results: In vitro treatment of EAC cells with egg extract and the purple fluid caused significant decreases in the number and viability of EAC cells associated with increases in EAC apoptosis in a dose-dependent manner as compared to untreated EAC cells. In vivo, both the purple fluid extract (20μg/ mouse) and egg extract (6.7 μg/mouse) significantly reduced the numbers of EAC cells by 4.3 and 2.3 folds, respectively. However, the anti-tumour effects of the extracts either in vitro or in vivo were yet lower than that of the anti-tumor reference drug cisplatin. Both extracts induced significant increases in the levels of relative and absolute numbers of lymphocytes, mature macrophages (CD11b⁺ Ly6G^-) while with minimal effects on immature neutrophils (CD11b⁺ Ly6G⁺). Conclusion: Both egg extract and the purple fluid of Aplysia fasciata possess potential anti-tumour effects with less toxicity, opening new avenues for further evaluation of the chemical and biological mechanisms behind these effects.