Our research group has held a long standing interest in developing chelation strategies to form mononuclear, trivalent rare earth coordination complexes. Here, I will discuss our recent advances in adapting a single chelator platform that enables diagnostic PET imaging with Y-86, intrasurgical resection guided by optical imaging at 620 nm with Eu, and low-dose radiotherapy with Tb-161. The development of a multifunctional platform requires that rare earth ions of disparate sizes are readily accommodated by the same chemical environment to form inert, in vivo compatible complexes; furthermore, the implementation of optical imaging with Eu requires that the chelator incorporates as a sensitizing antenna. We show that chelator optimization requires balancing of the optical properties of the Eu complex with minimization of complex lipophilicity to retain favorable pharmacokinetic properties. The lead construct is functionalized with a targeting peptide and validated in a murine xenograft model of prostate cancer.