Subjective well-being (SWB) is a desirable goal for the society as a whole and in particular for young adults (i.e., those aged 18–34) who are a crucial segment of a population. Their importance emerges not only as citizens of contemporary society, but also as citizens of the future society both as participants in democracies and as constituents of the economic labour force. At the same time, young adults are a very vulnerable group that has been particularly affected by the economic downturn. Therefore, young adults’ well-being is increasingly drawing the attention of European policymakers. This paper explores the determinants of SWB of young adults in Europe and examines especially the impact of institutional trust on the overall life satisfaction. Structural equation modelling was used to test main research hypotheses concerning the presence of a positive relation between level of trust and overall life satisfaction once psychological traits, evaluative indicators of specific aspects of life and the other individual characteristics are controlled for. Findings reveal interesting cross-country differences, providing useful policy implications.