A Tryptic Digested Abrus Agglutinin And Abrin Peptide Fractions Named Agp And Abp Respectively, Obtained From 10-Kda Molecular Weight Cut Off Membrane Permeate Were Found To Have Selective Antiproliferative Activity Towards Several Tumor Cell Lines In Vitro Without Having Any Cytotoxic Effect On Normal Cell Lines. The Peptide Fractions Induced Mitochondrial Apoptotic Pathway By Caspase-3 Activation Involving Mitochondrial Membrane Potential Damage And Reactive Oxygen Species Production. The Ld50 In Mice Was 50.0 And 2.250 Mg/Kg Body Weight Of Agp And Abp Respectively. The Acute Toxicity Of Peptide Fractions Was Determined With Sublethal Doses In Normal Mice. The Sublethal Doses Of Peptide Fractions Showed Very Significant Growth Inhibitory Properties In Vivo Dalton’s Lymphoma (Dl) And B16 Melanoma Bearing Mice. The Analysis Of Tumor Derived Dl Cells Showed Apoptotic Features. Further, Western Blot Showed Apoptosis Was Mediated By Reduction In Ratio Of Bcl-2 And Bax Protein Expression And Activation Of Caspase-3 Through Release Of Cytochrome C In Dl Cells. Regarding Immunostimulation In Tumor Bearing Mice, Both Agp And Abp Were Found To Activate Splenocytes And Induced Production Of Cytokines Like Il-2, Ifn-Γ And Tnf-Α Indicating A Th1 Type Of Immune Response. Analysis Of In Vitro Treated Splenocytes By Flow Cytometry Revealed An Increase In Percentage Of T And B Cell With High Expression Of Activation Markers (Cd25 And Cd71). At The Same Time, Expression Of Co-Stimulatory Marker Was Significantly Higher Compared To Control. On Treatment, The Tumor Associated Macrophages (Tam) Were Capable To Stimulate No Production, Il-1 Secretion, Increased Phagocytosis And Decreased Expression Of Mannose Receptor. It Was Also Observed That Natural Killer (Nk) Cell Was Activated By Agp And Abp. Both Peptide Fractions Did Not Show Any Hemagglutination Activity. The Maldi-Tof Analysis Of Peptide Fractions Showed Two Distinct Molecular Abundance Profiles With Molecular Weight In Range Of 500da To 1500da. Both Agp And Abp Found To Target Mitochondria Of Tumor Cells As Observed By Confocal Microscopy. Keywords: Abrus; Agglutinin; Abrin; Peptide; Hela Cells; Mitochondria; Apoptosis; Dalton’s Lymphoma; Melanoma; Antitumor; Immunostimulation; Sugar Binding