The single crystals of diaquabis(hydrogenmalonato)cobalt(II) were synthesized and grown using the slow evaporation of solutions method. The structure of the compound was obtained through single crystal XRD analyses and it belongs toP2(1)/cspace group of monoclinic system. The UV-vis absorption spectrum exhibits two peaks at 216 nm and 259 nm in the UV region and one peak at 524 nm in the visible region. Photoluminescence studies revealed emission of intense blue radiation. The thermal stability and decomposition stages have been investigated by TGA-DTA analysis. The magnetic measurements exposed that the compound exhibits antiferromagnetic behavior at low temperature.