Thermoelectric properties of Ni substituted (La) cobaltate compounds with perovskite structure have been investigated. For all the studied compounds the Seebeck coefficient is positive indicating predominant positive charge carriers. The electrical resistivity decreases considerably with increasing Ni content and with increasing temperature. The thermoelectric power factor was enhanced to 2.7 x 10(-4) W/K-2 m for samples with 10% Ni content at room temperature. The submicrograin morphology of the powders leads to a reduction of the thermal conductivity.