This article explores how assessment plays a role in helping learners to learn on a continuous, sustainable basis. It begins by exploring the paradigm of lifelong learning, which implies a shift in the way we think about learning and knowledge. Based on knowledge formation rooted in a flux of learning, lifelong learning assessment is not so much the assessment of how much fixed knowledge learners possess but rather the assessment of learners' abilities to reconstruct knowledge and engage with change. This article argues that three concerns--the primacy of self-assessment, the assessment of learners' engagement, and the importance of qualitative assessment--are crucial to an assessment which contributes to the development of lifelong learners who have the continuing ability to grow and to find deep and meaningful connections during times of change. The importance of self-assessment as the central aspect of lifelong learning is presented, and the way in which self-assessment relates to formative assessment and summative assessment to ensure a valid development of lifelong learning is considered. Judging whether lifelong learning is relevant or desirable requires learners' engagement in considering how they are holistically related to the world. To assess learners' overall engagement, this article suggests a multi-faceted, holistic approach which emphasises qualitative methods to track each individual's learning situation, although quantitative methods are not rejected. It is hoped that the article's discussion of this lifelong learning assessment will contribute to an understanding of the assessment's appropriate nature and development.