Malaria is a major public health problem in Papua New Guinea (PNG). The Artemisinin-based combination therapy is widely used as the first-line treatment for malaria in PNG. This study was to assess the quantity of the Artemether and Artesunate ingredients in the antimalarial drugs used for the treatment of malaria in the National Capital District (NCD) PNG. Artemether and Artesunate tablets were purchased from various pharmacies in NCD. Artemether and Artesunate solutions were prepared according to the Standard United States Pharmacopoeial protocol for assay of active ingredients by high performance liquid chromatography (HPLC). The results indicated that the percent Artemether content in the three brands (ART 01, ART 02 and ART 03) of Artemether purchased in the NCD were 93.2%, 87.6% and 89.3% respectively. Four brands (ATS 01/02, ATS 03/04, ATS 05, and ATS 06) of Artesunate were purchased in the NCD. The % Artesunate content in the four brands were 109.0%, 110.0%, 101.2% and 96.2%% respectively. The three Artemether brands (100%) and two (ATS 01/02 and ATS 03/04) of the Artesunate brands (50%) did not satisfy the USP specifications for the amount of active ingredients in the drugs. Our data indicate that poor quality Artemether and Artesunate antimalarial drugs are sold in the National Capital District in PNG. This indicates the urgent need to advocate for more efficient drug monitoring and effective enforcement of regulations that prevents importation of substandard drugs into the NCD.