He died, two months after a stroke, and after a period of mental decline believed to be caused by syphilis, in his club room in Welbeck Street, west London, in the Douglas Mausoleum outside Cummertrees Parish Church.
His divorces, brutality, atheism, and association with the boxing world made Queensberry an unpopular figure in London high society.
In 1882, he was ejected from the theatre after loudly interrupting a performance of the play The Promise of May by Alfred Lord Tennyson, the Poet Laureate, because it included a villainous atheist in its cast of characters.
Under the auspices of the British Secular Union, Queensberry wrote a pamphlet entitled The Religion of Secularism and the Perfectibility of Man.
He had three brothers, Francis, Archibald, and James, and two sisters, Gertrude and Florence.
He was briefly styled Viscount Drumlanrig following his father's succession in 1856, and on the latter's death in 1858 he inherited the Marquessate of Queensberry.
In 1866 he was one of the founders of the Amateur Athletic Club, now the Amateur Athletic Association of England, one of the first groups that did not require amateur athletes to belong to the upper-classes to compete.