An outbreak investigation of copra itch revealed a cluster of six suspected cases with skin dermatitis, with 11-32 years of age, belonging to a single family, between June and July 2016 in Phang Nga province, Southern Thailand. Epidemiologic investigation of these suspected cases revealed five probable cases developing multiple discrete erythematous papules with intense pruritus on the body rather than the extremities and one confirmed case whose skin was infested with domestic mite, Tyrophagus longior (Gervais) (Ascari: Ascaridae). This mite was also found in unused coir mattresses outside their bedrooms. Household infestation with T. longior mites rendered these family members to become more susceptible to expose indoor biting of T. longior adult mites that were adapted well to the domestic environments with poor hygienic conditions. Human exposure to mite bites was more likely to be a direct contact than an indirect contact. Findings from this copra itch outbreak investigation provided understanding of natural disease of copra itch and factors that favored the outbreak, and could guide diagnosis for physicians, surveillance and response for surveillance and rapid response teams (SRRTs), and prevention and control for entomologists and public health personnel.