Purpose: To increase the solubility of artemether (ART) in Transcutol® HP through microencapsulation in sodium alginate polymer to achieve  sustained in vivo release.Method: Graded concentrations of ART (0.00, 0.25, 0.50, 0.75, and 1.00 g) microcapsules were produced using Tween® 80 by the cold  homogenization method at 24 x 1000 rpm for 15 min. Characterization based on yield, encapsulation efficiency (EE), particle size, pH stability,  differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and in vivo release using Peter’s four-day suppressive protocol in Wistar mice infected with Plasmodium berghei, were determined.Results: The results obtained indicate that 0.5 g ART-loaded microcapsules (AMC) showed the highest yield of 96.85 %. The EE of 88.3 %  corresponded to 0.75 g ART-loaded microcapsules. DSC results revealed that there was a significant reduction in enthalpy in all the formulations compared to the crystalline drug, but no strong bond interaction occurred except for the blank microcapsules. The AMC1.0 showed high dose-dependent plasmodial growth inhibition of 88.75 % while AMC0.25 had the least (68.13 %).Conclusion: The artemether microcapsules showed sustained release characteristics for oral delivery of artemether and therefore may reduce some of the adverse effects associated with high dose artemether therapy in conventional oral tablets. Keywords: Malaria, Artemether, Transcutol® HP, Sustained-release, RBC count, Antiplasmodial activity