Gentlemen visitors to Whitehall often gathered in the Billiard Room for entertainment, much as the women used the Drawing Room for conversation and music. Reflecting the Gilded Age interest in sport, billiards became popular with men of the period and most estates included similar game rooms. Flagler recognized the importance of having a room dedicated to the sport and in a letter to Stymus dated 1901, he wrote, "I have enlarged the billiard room considerably from the original plans." In another letter to Stymus, Flagler ordered two spitoons, or cuspidors, for the Billiard Room, one for each of the Offices and one for the Library, commenting, "Mrs. Flagler says she doesn't want any elsewhere in the house." Spitoons were a common feature of homes of this period.
A Caen Stone mantle with Swiss-style decoration is the predominate feature of the room. The Billiard Room's molded plaster ceiling is painted to reflect the Swiss design of the room, with plain panels painted to look like zebra oak, popular at the time.