Synthesis and electrical and thermal transport properties are reported for several filled skutterudite compounds doped with Ni: Ba0.3NixCo42xSb12 with 0,x,0.2. Divalent Ba readily fills the cages of the skutterudite structure and is effective in reducing the thermal conductivity of the structure. The presence of a small amount of Ni increases the electron concentration, further reduces the thermal conductivity, and enhances the thermoelectric power factor. Hall mobility studies indicate that the addition of Ni to the system has the effect of increasing the relative strength of ionized impurity scattering as compared to acoustic phonon scattering. These results suggest that doping with Ni is an attractive avenue to optimization of filled skutterudites. The dimensionless thermoelectric figure of merit ZT was observed to increase from a value of 0.8 at 800 K for Ba0.3Co4Sb12 to a value of 1.2 for the sample with x50.05. These materials show considerable potential as n-type legs in thermoelectric power generation at elevated temperatures.