Background: The efforts to find alternative antimalarial medicine have not essentially solved the problem of malaria control because of the presence of medication resistance. The Plasmodium resistance to antimalarial medicine is resulted from malaria treatment failure. Therefore, the availability of new antimalarial medicine is urgently needed to overcome the resistance problems. Coptosapelta tomentosa is empirically used by people in Kotabaru South Kalimantan as part of the treatment for Malaria. Objective: The aim of this research was to determine IC50 value of in vitro antiplasmodial activities from ethanol extract of C. tomentosa roots. Methode: Coarse powder of C. tomentosa roots was extracted using ethanol 96% by maceration method. An in vitro antiplasmodial activity test was carried out by using Candle Jar method. The doses of administration of ethanolic extract of C. tomentosa roots were at 500; 250; 50; 25; 5; dan 0.5 μg/mL concentration. Results: The results of the study included parasitemia percentage, P. falciparum growth inhibition percentage and IC50 value. The IC50 value of the ethanol extract of C. tomentosa roots was 2.46 μg/mL. Conclusion: The in vitro antiplasmodial activities of ethanol extracts of C. tomentosa roots were categorized to be very active. Keywords: Captosapelta tomentosa; Manuran; in vitro antiplasmodial activity; Borneo; Kalimantan