We have studied some of the nuclear decay properties of 58 Co m . The half-life is found to be (8.853 ± 0.023) hours, which is significantly different from the evaluations found in the literature. The absolute intensity of the 24.9-keV γ-ray emitted in the IT decay is (0.0387 ± 0.0016)%, in agreement with the calculated yield of a transition of M 3 multipolarity. We observe γ-ray photons from a previously unreported branch for EC decay, with an intensity of (0.00120 ± 0.00005)%, consistent with expectations from the calculation of log f t.