This book constitutes the thoroughly refereed post-workshop proceedingsof the Second International Workshop on Languages, Methodologies, andDevelopment Tools for Multi-Agent Systems, LADS 2009, held in Torino, Italy, in September 2009 - as part of MALLOW 2009, a federation ofworkshops on Multi-Agent Logics, Languages, and Organizations.The 10 revised full papers presented were carefully selected during tworounds of reviewing and improvement from 14 initial submissions. Thepapers are organized in topical sections on agent architectures, agentprogramming languages and methodologies, social interaction models, development tools for multi-agent systems, and applications.