The electron’s kinetic energy plays a pivotal role in magnetism. While virtual electron hopping promotes antiferromagnetism in an insulator, real hopping processes usually favour ferromagnetism. However, in kinetically frustrated systems such as hole-doped triangular lattice Mott insulators, real hopping has instead been shown to favour antiferromagnetism. Kinetic frustration has also been predicted to induce a new quasiparticle, a bound state of the doped hole and a spin flip called a spin polaron, at intermediate magnetic fields, which could form an unusual metallic state. Here we report the direct observation of spin polarons in triangular lattice MoTe2/WSe2 moiré bilayers. A spin polaron phase emerges at a lattice filling factor just below 1 and is separated from the fully spin-polarized phase by a metamagnetic transition. We determine that the spin polaron is a spin-3/2 particle and that its binding energy is commensurate with the kinetic hopping energy. Our results will enable the exploration of spin polaron pseudogap metals, spin polaron pairing and other new phenomena in triangular lattice moiré materials.