Although Winston wished his son to marry the wealthy Catherine Sedley (if only to ease his own burden of debt), Colonel Churchill married Sarah sometime in the winter of 1677–78, possibly in the apartments of the Duchess of York.
Selv om Sir Winston ønskede, at hans søn skulle gifte sig med den velhavende Catherine Sedley (om ikke andet så for at lette hans egen gældsbyrde), giftede oberst Churchill sig hemmeligt med Sarah en gang i løbet af vinteren 1677–78, muligvis i hertuginden af Yorks bolig.