We have investigated the structural and magnetic properties of the new intermetallic compounds RNiSi3 (R = Dy, Ho) grown by the Sn-flux method, which yields high quality single crystals. X-ray powder diffraction data show that these compounds crystallize in a layered or- thorhombic structure (SmNiGe3-type). Temperature dependent magnetization between 2 K and 310 K is anisotropic and reveals that the ground states are antiferromagnetic. Low-temperature magnetic isotherms up to H = 70 kOe exhibit multiple metamagnetic transitions and alternating reversible–irreversible regions in the ordered state, which are dependent on temperature, magnetic field and crystal orientation. From this complex magnetic behavior we have built tentative magnetic phase diagrams for the two compounds.