The thermoelectric properties of quasi‐1D electron waveguides at the LaAlO₃/SrTiO₃ interface at millikelvin temperatures are investigated. A highly enhanced and oscillating thermopower is found for these electron waveguides, with values exceeding 100 μV K⁻¹ at 0.1 K in the electron‐depletion regime. The Mott relation, which governs the band‐term thermopower of noninteracting electrons, agrees well with the experimental findings in and around regimes where strongly attractive electron–electron interactions lead to a previously reported Pascal series of conductance explained by bound states of electrons. These results pave the way for quantized thermal transport studies of emergent electron liquid phases in which transport is governed by quasiparticles with charges that are integer multiples or fractions of an electron.