Artemisia herba-alba Asso (Asteraceae), commonly known as wormwood, is a perennial flowering herb native to the arid and semi-arid zones of the Mediterranean basin and a rich source of phytochemicals, including artemisinin derivatives. These sesquiterpene lactones are of major medicinal importance, and artemisininbased therapies are used against chloroquine-resistant Plasmodium falciparum. Because the yield of these phytochemicals depends on the environmental and cultivation conditions, this study aimed to determine the percentage of artemisinin derivatives in the leaves of A. herba-alba collected from the Diyala governorate, Iraq, and to assess whether the local conditions are favorable for the plant. The aerial parts were harvested twice, in spring (April) and summer (July) 2024. The leaves were separated, dried in the dark, and pulverized, and a hexane extract was prepared by cold maceration and evaporated to dryness. The extract was screened for six Artemisia terpenoids — artemisinic acid, arteannuin B, dihydroartemisinin, artemisitene, artemisinin, and deoxyartemisinin — by reversed-phase high-performance liquid chromatography (RP-HPLC), and the percentage of each compound in the leaves was calculated from the extraction yield. The extraction yield was 0.85% for the April sample and 3.85% for the July sample, and the leaf content of the measured compounds was markedly higher in the July (summer) sample — approximately eight times that of the April (spring) sample. The summer artemisinin content approached the upper part of the range previously reported for Artemisia (0.01–0.8% in A. annua). These results indicate that summer is the optimal harvesting season and that A. herba-alba grown in the Diyala governorate can serve as a promising source of artemisinin derivatives, warranting measures to improve and exploit its yield.