Thermoelectric (TE) properties of erbium-silicon co-doped In xGa 1-xN alloys (In xGa 1-xN: Er + Si, 0≤x≤0.14), grown by metal organic chemical vapor deposition, have been investigated. It was found that doping of InGaN alloys with Er atoms of concentration, N[Er] larger than 5×10 19 cm -3, has substantially reduced the thermal conductivity, κ, in low In content InGaN alloys. It was observed that κ decreases as N[Er] increases in Si co-doped In 0.10Ga 0.90N alloys. A room temperature ZT value of ∼0.05 was obtained in In 0.14Ga 0.86N: Er + Si, which is much higher than that obtained in un-doped InGaN with similar In content. Since low In content InGaN is stable at high temperatures, these Er+Si co-doped InGaN alloys could be promising TE materials for high temperature applications.