The biosynthesis of the major acyl carrier Coenzyme A from pantothenic acid (PA) is critical for survival of Plasmodium falciparum within human erythrocytes. Accordingly, a PA analog alpha-PanAm showed potent activity against blood stage parasites in vitro; however, its efficacy in vivo and its mode of action remain unknown. We developed a new synthesis route for alpha-PanAm and showed that the compound is highly effective against blood stages of drug-sensitive and -resistant P. falciparum strains, inhibits development of P. berghei in hepatocytes, and at doses up to 100 mg/kg also inhibits blood stage development of P. chabaudi in mice. We used yeast and its pantothenate kinase Cab1 as models to characterize mode of action of alpha-PanAm and found that alpha-PanAm inhibits yeast growth in a PA-dependent manner, and its potency increases dramatically in a yeast mutant with defective pantothenate kinase activity. Biochemical analyses using C-14-PA as a substrate demonstrated that alpha-PanAm is a competitive inhibitor of Cab1. Interestingly, biochemical and mass spectrometry analyses also showed that the compound is phosphorylated by Cab1. Together, these data suggest that alpha-PanAm exerts its antimicrobial activity by direct competition with the natural substrate PA for phosphorylation by the pantothenate kinase.