We report high-resolution anion photoelectron spectra of thiozonide (S-3(-)) acquired by slow electron velocity-map imaging (SEVI). The ions were cryogenically cooled within an ion trap before photodetachment. We measure an electron affinity of 2.3630(9) eV, resolving discrepancies in previously reported photoelectron spectra that resulted from the presence of vibrational hot bands. The SEW spectrum shows well-resolved, extended vibrational progressions in the symmetric stretch and bending modes of S-3, yielding accurate frequencies for both.