Theranostic agents that combine diagnostic imaging and targeted therapy are reshaping how we detect and treat cancer. In this work, we introduce a newly synthesized pyrazolone-based compound, designed with sustainability in mind using a green synthetic route. The ligand, 5-(2-hydroxyphenyl)-2,4-dichloro-3H-pyrazol-3-one, was structurally confirmed and efficiently radiolabeled with the copper isotopes ⁶⁴Cu and ⁶⁷Cu enabling both PET imaging and therapeutic functions. Under optimized conditions, the radiocomplex demonstrated excellent labeling yield and serum stability, along with a favorable lipophilicity profile. In vivo biodistribution studies in tumor-bearing mice revealed strong and selective tumor uptake, achieving a T/NT ratio of 6.58 ± 0.03 shortly after administration. Docking simulations suggested possible therapeutic relevance through favorable interactions with cancer-associated targets. These …