A single-crystal electron paramagnetic resonance (EPR) spectroscopic investigation of Mn(II)-doped dipotassium diaquabis(malonato-κ 2 O,O ) zincate dihydrate has been carried out at X-band frequencies at 300 K. The EPR spectrum at room temperature exhibits more than 30 lines along a crystallographic axis, suggesting the presence of two types of impurities in the lattice. Single crystals, rotated along the three mutually orthogonal axes, have yielded the spin-Hamiltonian parameters g, A and D as g x x = 2.049, g yy = 2.005, g zz = 1.993; A x x = −9.17, A yy = −8.36, A zz = −8.06 mT; D x x = 31.55, D yy = 7.13, D zz = −38.68 mT, respectively. The other site, due to its low intensity, could not be followed during crystal rotations. The optical absorption spectrum contains characteristic bands of Mn(II) ions in distorted octahedral symmetry. From the observed optical spectrum, the crystal field parameters have been evaluated.