In this study, we showed the crystal structure, electric resistivity, Seebeck and Hall coefficients, magneto-resistance, and magnetic susceptibility of Pr1−xCaxBa2Cu4O8 (x= 0.0, 0.02, and 0.05) are all relevant for our understanding of physical properties along CuO double chains. The lattice parameters of Ca substituted PrBa2Cu4O8 remained almost invariant up to x= 0.05. Contrary to the Ca doping effect in the PrBa2Cu3O7−δ system, the significant increases in the Seebeck and Hall coefficients due to the Ca substitution indicate a decrease in the carrier number. The significant magneto-resistance effect in the parent sample (16% at 10 K) was significantly reduced down to 5% in the x= 0.05 composition. On the basis of the two types of carrier models, we discussed the influence of Ca substitution on the electrical transport and magneto-transport properties.