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The electrical resistivity ρ and thermopower S of the cubic Laves phase compounds Ho(Co 1−x Al x ) 2 (x = 0, 0.15 and 0.20) have been measured at temperatures from 2 K to 300 K in magnetic fields up to 10 T. The measurements of ρ under pressures up to 3 GPa have been performed in the temperature range between 2 K and 300 K. Both ρ(T ) and S (T ) of the pure HoCo 2 reveal abrupt changes at the magnetic ordering temperature T C , indicating the first order transition. ρ(T ) of the Al substituted samples (x = 0.15 and 0.20) show anomalous behavior in the form of an increase below T C . The variations of ρ and S at T C clearly indicate that the type of the magnetic transition changes under substitution of Al for Co from the first order to the second order. The residual resistivity of Ho(Co 1−x Al x ) 2 shows a rapid increase with increasing x. T C increases linearly for x < 0.15, having a maximum at x ≈ 0.15 and decreases with further increase of x. The peculiar x dependence of T C and the anomalous behavior of ρ(T ) and S (T ) around T C are related to the metamagnetic instability of Co 3d subsystem and to fluctuating local magnetic susceptibility due to the atomic substitution.