The adsorption of the dye (rhodamine-B) by natural diatomite was investigated. It was found that natural diatomite is an effective adsorbent for removal of Rh-B from wastewater due to its short adsorption time and its natural pH (8.0±2). The thermody-namic parameters (ΔGo, ΔHo and ΔSo) were calculated. It was shown that adsorption of Rh-B dye by natural diatomite is both endothermic and spontaneous. The removal of Rh-B by the natural diatomite was controlled by the initial dye concentration at natural pH and different temperatures. The adsorption data were well fitted by both Langmuir and Freundlich models. The maximum adsorption was found to be 10.21 mg/g (for initial concentration 20 mg/dm3, temperature 323 K). The adsorption kinet-ics of Rh-B can be well described by the pseudo-second-order model. As a result, the natural diatomite can be used as a highly effective low-cost adsorbent for the removal of Rh-B from an aqueous solution.