A quadruple perovskite LaMn3Rh4O12 with A' = Mn and B = 4d transition metal was synthesized at high pressure (8 GPa) and temperature (1423 K) for the first time. Room temperature powder X-ray diffraction indicates that LaMn3Rh4O12 forms in cubic symmetry (Im (3) over bar, a = 7.4997(1) angstrom). X-ray absorption near-edge spectroscopy shows predominantly Mn3+ and Rh3+ oxidation states. An antiferromagnetic transition at T-N similar to 41 K is corroborated by specific heat measurements. The resistivity measurements indicate a three-dimensional Mott variable-range hopping conduction mechanism between 300 and 160 K.