This book constitutes the thoroughly refereed post-workshop proceedings of the Third International Workshop on Languages Methodologies and Development Tools for Multi-Agent Systems LADS 2010 held in Lyon France in August/September 2010 as part of MALLOW a federation of workshops on Multi-Agent Logics Languages and Organizations. The 8 revised full papers presented were carefully selected during two rounds of reviews from 11 initial submissions. The papers address issues related to theories methodologies models and approaches that are needed to facilitate the development of multi-agent systems ensuring their predictablity and verification.