Solution-focused coaching and solution-focused therapy are strengths-based approaches which emphasize people's resources and resilience and how these can be used in the pursuit of purposeful, positive change. The Solution-focused Inventory (SFI) is a 12-item scale with three subscales: Problem Disengagement, Goal Orientation and Resource Activation. Three studies in this article provide support for the validity of the SFI as a measure of solution-focused thinking. The SFI negatively correlated with psychopathology and positively correlated with measures of well-being, resilience and perspective taking. Test-retest reliability over 16 weeks was 0.84. Cronbach's alpha for the 12-item scale was 0.84. It also demonstrates sensitivity to purposeful change in that participation in a leadership development coaching intervention was associated with significantly increased scores on the SFI, whilst scores for the control group did not change.