The grooming behaviors of the Hawaiian river shrimp, Macrobrachium grandimanus (Caridea: Palaemonidae), are examined in this study. This species has a dense aggregation of setae (termed the “setal patch”) located on the major second cheliped. The function of this setal patch is unknown but hypothesized to be utilized in grooming activities. The grooming behaviors were documented in terms of appendages used to groom, groomed body areas, type of grooming behavior (pick, brush, or scrape) and a time budget for grooming. The most frequently used grooming appendages are the third maxillipeds and first pereiopods, while the most frequently groomed body region is the antennules. The most frequently used grooming behavior is a scraping action; the body region groomed for the longest amount of time is the branchiostegite (gill cover) region where the gill chamber is located. The time budget for grooming was 24.7%, which suggests approximately six hours per day are dedicated to grooming. Multiple statistical analyses of the grooming behaviors of M. grandimanus indicate the setal patch is not associated with grooming either as a grooming appendage, or a groomed body region. Ideas for possible functions of the setal patch are presented.