As-based Zintl compounds Bai(1-x)K(x)Zn(2)As(2) were prepared by solidstate reaction followed by hot pressing. Bai(1-x)K(x)Zn(2)As(2) (x < 0.02) crystallizes in the alpha-BaCu2S2-type structure (space group Pnma) upon cooling from 900 degrees C, whereas it crystallizes in the ThCr2Si2-type structure (space group 14/mmm) for x >= 0.04. The lattice thermal conductivities are almost equivalent for both crystal structures with relatively low values of 0.8-1.1 W/mK at 773 K. The values are comparable to those of Sb-based Zintl compounds, though Bai(1-x)K(x)Zn(2)As(2) consists.of As atoms, which are lighter than Sb atoms. The electrical resistivity and Seebeck coefficient decreases with increasing x, indicating successful hole doping by K substitution. The dimensionless figure-of-merit ZT is 0.67 at 900 K for x = 0.02, opening a new class of thermoelectric materials with the As-based 122 Zintl compounds.