Elphinstone was one of the first to join Charles Edward Stuart during his 1745 attempt to recover the British throne for the Stuarts. While his history of Jacobite activity was undoubtedly a factor, some contemporaries also suggested the family's poor financial standing meant he had little to lose. Alongside David Wemyss, Lord Elcho he was given command of a troop of Charles' "Life Guard"; unlike nearly all other senior Jacobites, he escaped any criticism in the post-rising memoirs by various participants. John Daniel, a colleague in 1745, recorded that Elphinstone's "sole and predominant passion" was "hard drinking", but paid tribute to his loyalty, courage, and gift for languages, noting that "his memory for his years was wonderful". He became the 6th Lord Balmerino in early 1746 following his half-brother James's death, but in April of the same year he was taken prisoner at the Battle of Culloden.