This bookconstitutes the revised selected papers of the Third International Conferenceon Networked Systems, NETYS 2015, held in Agadir, Morocco, in May 2015. The 29full papers and 12 short papers presented together with 22 poster abstractswere carefully reviewed and selected from 133 submissions. They address majortopics such as multi-core architectures; concurrent and distributed algorithms;middleware environments; storage clusters; social networks; peer-to-peernetworks; sensor networks; wireless and mobile networks; and privacy andsecurity measures.