Layered nickelates have the potential for exotic physics similar to high T C superconducting cuprates as they have similar crystal structures and these transition metals are neighbors in the periodic table. Here we present an angle-resolved photoemission spectroscopy (ARPES) study of the trilayer nickelate La4Ni3O10 revealing its electronic structure and correlations, finding strong resemblances to the cuprates as well as a few key differences. We find a large hole Fermi surface that closely resembles the Fermi surface of optimally hole-doped cuprates, including its [Formula: see text] orbital character, hole filling level, and strength of electronic correlations. However, in contrast to cuprates, La4Ni3O10 has no pseudogap in the [Formula: see text] band, while it has an extra band of principally [Formula: see text] orbital character, which presents a low temperature energy gap. These aspects drive the nickelate physics, with the differences from the cuprate electronic structure potentially shedding light on the origin of superconductivity in the cuprates.Exploration of the electronic structure of nickelates with similar crystal structure to cuprates may shed a light on the origin of high T c superconductivity. Here, Li et al. report strong resemblances and key differences of the electronic structure of trilayer nickelate La4Ni3O10 compared to the cuprate superconductors.