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We present the results for the electronic structure and thermoelectric properties of La₃Te₄, Ce₃Te₄, and Pr₃Te₄, using first principles computation and Boltzmann’s transport equation. The effect of 4f electrons on the electronic and thermoelectric properties is investigated. We found that even though the presence of 4f electrons results in significant changes in the electronic structures, it does not always lead to an increase in thermoelectric properties as expected. The large increase in thermoelectric properties only occurs when the Fermi energy for the experimental value of the electron density is close enough to the resonance in the density of states such that band contributions to figure of merit ZT become dominant.