Sodium copper chlorophyllin (chlorophyllin, CHL), a semi-synthetic water-soluble derivative of green plant pigment chlorophyll, is associated with potential health benefits; however, systematic preclinical evaluation of its pharmacological and therapeutic potential remains limited. This study investigates safety, toxicology, pharmacokinetics, and efficacy of CHL as an adjunct to breast cancer chemotherapy. Acute and sub-acute oral toxicity of CHL was assessed in mice and rats under Good Laboratory Practice (GLP) conditions following OECD guidelines. Anti-cancer effects and mechanisms were evaluated in 4 T1mouse breast cancer cells using viability assays, colony formation analysis, and proteomics. Cyclophosphamide (CYP)-induced painful bladder syndrome (PBS) was studied in C57BL/6 female mice. In acute toxicity study, up to 5000 mg/kg bw of CHL was well tolerated without any signs of toxicity and death. In the sub-acute toxicity study, no features suggestive of drug-induced toxicity indicated No-Observed Adverse Effect Level (NOAEL) to be beyond 1000 mg/kg bw. CHL showed wide biodistribution, achieving sustained therapeutic concentrations in target tissues. CHL enhanced the anti-proliferative and cytotoxic effects of CYP in 4 T1 breast cancer cells, and proteomics studies revealed disruption in DNA damage repair, microtubule dynamics, and mitochondrial biogenesis, leading to apoptosis. CHL (100 mg/kg bw, oral) showed significant therapeutic benefit for treatment of CYP induced PBS. CHL alleviated PBS symptoms by restoring IL- 22 levels, reducing oxidative stress, and improving bladder functionality. Chlorophyllin appears to be relatively safe even at high doses, demonstrates potentially favorable pharmacology, and may hold promise for mitigating CYP-induced bladder toxicity and enhancing chemotherapy efficacy.