The factors affecting search guidance to categorical targets are largely unknown. We asked how visual similarity relationships between random-category distractors and two target classes, teddy bears and butterflies, affects search guidance. Experiment 1 used a web-based task to collect visual similarity rankings between these target classes and random objects, from which we created search displays having either high-similarity distractors, low-similarity distractors, or mixed displays with high, medium, and lowsimilarity distractors. Subjects made faster manual responses and fixated fewer distractors on low-similarity displays compared to high. On mixed trials, first fixations were more frequent on high-similarity distractors (bear=49%; butterfly=58%) than low-similarity distractors (bear=9%; butterfly=12%). Experiment 2 used the same high/low/mixed conditions, but now these conditions were created using similarity estimates from a computer-vision model that ranked objects in terms of color, texture, and shape similarity. The same patterns were found, suggesting that categorical search is indeed guided by visual similarity.