Introduction: Rhodomyrtus TOMENTOSA (haramonting), a typical plant of North Sumatera, Indonesia, contains important medicinal ingredients. Nano sized drugs have high loading capacities and can be given at high concentrations. This study aimed to determine the components and toxicity of nanoherbal haramonting. It also aimed to determine the effect of nanoherbal haramonting on the histology of the liver, kidneys, lungs, heart and brain. Methods: High-energy milling was performed to produce nanoherbal haramonting. Thinlayer chromatography was utilised to determine the chemical components of the nanoherb. Antioxidant tests were performed by using the 1, 1-diphenyl-2-picryhydrazil method. The three-stage of lethal dose 50 (LD50) which comprised the dose orientation test, preliminary test and actual phase test/LD50 determination, and the Thomson– Weil formula was applied to measure the lethal concentration 50 (LC50) of nanoherbal haramonting. Organs were collected for histological investigation after 14 days of the lethality test. Results: Nanoherbal haramonting had an average diameter distribution of 600. 1 nm ± 135. 8. It contained flavonoids, steroids, glycosides, saponins and tannins. Its LC50 and LD50 values were 2961. 535 ppm and 10. 4 ± 0. 135 mg/kg BW, respectively. The histology of the heart, kidney, lungs, heart and brain were changed and affected by nanoherbal haramonting treatment at each dose level. Conclusion: Nanoherbal haramonting has strong antioxidative activity and small size, can be effectively used as medicine in the future because it contains secondary metabolite compounds that can be developed as drugs. However, it has mild toxicity.