Humankinds use plants for the treatment of different health ailments, including malaria, since ancient times. Among these medicinal plants used to treat malaria in traditional medicine in Ethiopia and elsewhere is Brassica nigra. The medicinal effect of the plant is mainly confined to its seeds. Hence, this book discusses the preparation, extraction, chemosuppressive, and chemoprophylactic antimalarial activities of the seeds of Brassica nigra against Plasmodium berghei infection in mice. The 80% methanolic crude extract of the seeds of Brassica nigra showed good chemosuppressive and moderate chemoprophylactic antimalarial activities against Plasmodium berghei infection in mice. In addition, the seed extract of the plant increases the survival times and weight of mice. The plant may contain biologically active principles which are relevant in the treatment and prophylaxis of malaria. Further phytochemical, toxicological, and pharmacological investigations are, therefore, required to evaluate its full antimalarial potential.