This volume contains 11 thoroughly refereed and revised papers detailing recent advances in research on designing trading agents and mechanisms for agent-mediated e-commerce. They were originally presented at the Joint Workshop on Trading Agent Design and Analysis (TADA 2012) and Agent-Mediated Electronic Commerce (AMEC 2012) co-located with AAMAS 2012 in Valencia, Spain, in June 2012. The increasing reliance on software agents has created a range of pressing new research challenges, including the design of appropriate agent decision algorithms, approaches for predicting the complex...