We investigated the effects of Ni doping on carrier density and anomalous electrical transport properties in CeCo₁₋ₓNiₓIn₅ (x ≤ 0.3) by performing Hall resistivity measurements. The carrier density, estimated from the Hall coefficient R_(rm H) at a temperature of 0.5 K in high magnetic fields, increases linearly with x, indicating that the doped Ni ions act as electron dopants. In CeCoIn₅, the magnitude of -R_(rm H) is strongly enhanced at magnetic fields near the superconducting upper critical field H_c2 and in the low-field region above the superconducting transition temperature T_c. However, these anomalies are found to be significantly suppressed by Ni doping. Possible origins of this suppression in -R_(rm H) are discussed.