Solid-state reaction of praseodymium (Ⅲ) oxide, K_2CO_3 and MoO_3 at high temperature leads to a potassium lanthanide double molybdate, namely, KPr(MoO_4)_2. The structural and optical properties of the title compound have been investigated by means of single-crystal X-ray diffraction and spectroscopic measurements at room temperature. KPr(MoO_4)_2 crystallizes in tetragonal, space group I4_1/a with a = 5.401(3), c = 12.044(10), Z = 2 and R(I> 2σ(I)) = 0.0416. It features the famous scheelite-type structure (CaWO_4), which can be thought as the substitution of two Ca~(2+) ions in CaWO_4 by a couple of K~+ and Pr~(3+) ions in a statistical manner, and W~(6+) by Mo~(6+) cations.