Scientific conferences are a widely established and a highly important and an indispensable component for knowledge sharing, networking activities, scientific debate etc. What is usually ignored is the resource demand of such an event, putting an enormous burden on the environment. For almost two decades now, there has been an increasing demand for mitigation of environmental impacts of scientific conferences. In the field of sustainability science hardly any measures have been taken as only one out of ten sustainability conferences promoted action to reduce environmental impacts. A comprehensive Life Cycle Assessment (LCA) has not been carried out for all phases of a conference. This study therefore strives to conduct a comprehensive LCA of a scientific conference held on sustainability topics. The assessment includes three main parts: 1) preparation of the conference, 2) conference execution, and 3) further pre-/post-conference activities (participants´ travel associated with the conference). The functional unit is defined as: Holding one 3-day international academic conference on sustainability topics. The results display that travel activities of participants dominantly contribute to the overall environmental impact. Further relevant phases are catering, hotel overnight stays as well as environmental burdens associated with the conference venue. It was found that the conference under consideration leaves a carbon footprint of 455 tonnes of CO2 eq., equivalent to an average of 0.57 tonnes per participant. A scenario analysis displayed that changes towards train travelling, vegetarian meals and reduction of conference materials can significantly better the environmental profile of a conference. Further measures of environmental optimization could be identified, e.g. digital meetings. It is however unlikely that those will totally replace physical meetings. The social benefits of direct personal and globally-oriented exchange can probably not be outweighed by environmental savings. Future conference planning should thus relate the sustainability benefits with the detrimental impacts.