This article uses the broad concept of ‘improvement of minds’ to refer to the idea of improving people's sense of morality, their ability and willingness to reason, and the depth of their emotional experiences. Such an objective has been little explored in the context of the history of the British Labour party. Yet, discussion of it is worth integrating into histories of the party for two reasons. First, the goal of improving minds was a strand – though often unsystematically developed – in the agendas of many Labour party politicians, activists, and thinkers. Secondly, the very fact that it was an unsystematically developed strand, the very limits of the party's attention to, and success in achieving, ‘mental progress’ amongst the twentieth-century British population – that is to say, simply, the limits to the party's pursuit and achievement of the objective of making people more caring, rational, and sensitive – is one important explanation for many of Labour's failures. The article begins to explore the aims, processes, and outcomes of Labour's attempts to improve minds, as well as to explain and examine the consequences of the limits of the party's attention to this goal, through the case study of Tony Crosland.