Heightened parasite resistance urges the need for new therapeutic agents to treat diseases like leishmaniasis. Previously, extracts from ginseng exhibited antiprotozoal effects against malaria, trypanosomiasis, and leishmaniasis. In this study, we evaluated the antileishmanial activity of Korean red ginseng extract (KRGE) using the Alamar Blue assay on promastigotes and axenically cultured amastigotes from clinical isolates of Leishmania aethiopica and Leishmania donovani. Amphotericin B served as the positive control, while 1% dimethyl sulfoxide (DMSO) and the culture medium were used as negative controls. Our results indicated that KRGE has a significant dose-dependent inhibition with IC ₅₀ values of 18.09 ± 1.64 and 17.22 ± 0.47 µg/ml for promastigotes, and 14.06 ± 0.09 and 15.45 ± 0.33 µg/ml for axenic amastigotes of L. aethiopica and L. donovani, respectively. Moreover, KRGE exhibited selectivity indices (SIs) of 3.18 and 3.34 for promastigotes, and 4.09 and 3.72 for amastigotes, whereas amphotericin B had SIs of 34.05 and 32.70 for promastigotes, and 32.15 and 31.28 for amastigotes. Altogether, KRGE possesses promising antileishmanial activity against L. aethiopica and L. donovani, warranting further investigation using active compounds isolated form Korean red ginseng.