Non-human animal genomes, non-human animal cells, and non-human animals comprising a humanized albumin (ALB) locus and methods of making and using such non-human animal genomes, non-human animal cells, and non-human animals are provided. Non-human animal cells or non-human animals comprising a humanized albumin locus express a human albumin protein or a chimeric albumin protein, fragments of which are from human albumin. Methods are provided for using such non-human animals comprising a humanized albumin locus to assess in vivo efficacy of human-albumin-targeting reagents such as nuclease agents designed to target human albumin.