Single crystals of potassium penta berate (KB5) exhibit interesting non-linear optical properties such as phase-matched second-harmonic generation of the light for a wavelength as short as 216.8 nm. In the present work, single crystals of KB5 with dimensions upto 20 x 20 x 8 mm(3) are grown by slow evaporation method and subjected to X-ray, TGA, DSC and microhardness studies. The thermogravimetric analysis confirms the decomposition of KB5 taking place in two stages. The DSC curve of KB5 crystals are recorded in the temperature range 50-580 degrees C. The phase transition temperatures and enthalpies of KB5 were measured and the results are discussed. The grown crystals of KB5 are subjected to microhardness studies using a Vickers diamond pyramid indentor. The microhardness measurements carried out on the (0 1 0), (1 0 0) and (0 0 1) orientations confirm the anisotropic nature in the microhardness number values.