In pets, as in humans, there is increasing interest in interventions that promote ‘health and well-being’ into later life and extend these beyond their current limits. The purpose of this review was to assess the relevance of current knowledge of ageing in humans, described in a companion paper, as well as reviewing recent research on ageing in pet populations. The role of diet and other factors that influence the ageing process and ultimately lifespan in pets are highlighted in this review; in addition, future opportunities and challenges to further our understanding of the ageing process in pets are identified. Advancing knowledge of the fundamental biology of ageing will be key for the development and evaluation of strategies that extend both the quality and the quantity of lifespan in human and pet populations.