Seventeenth-century British preachers persistently defined hypocrisy in contrast to its divine antidote: sincerity. This article looks at four such case studies from across the ‘puritan’-‘Anglican’ divide, analysing the sermons of the Independent Nicholas Lockyer, the Presbyterian Christopher Love, the Church of England clergyman James Oldfield, and the archbishop of Canterbury John Tillotson. It considers to what extent Protestant instruction on sincerity and hypocrisy shifted according to religious affiliation and socio-political context, arguing that although these sermons possessed considerable continuities in their theological underpinnings, they also exhibited divergences in focus and instruction that are sometimes, but not always, predictable along denominational lines. These differences held weighty implications for the individual receiving spiritual guidance on how to forswear hypocrisy and live a truly sincere life, particularly throughout the period of instability and contention that marked Britain from the Civil Wars to the Glorious Revolution.