On December 31, 1930, in need of money, he turned professional and joined the fledgling pro tour, which had begun only in 1927. For the next 15 years, he and a handful of other professionals such as
Hans Nüsslein and
Karel Koželuh barnstormed across the United States and Europe in a series of one-night stands, with Tilden still the player that people primarily paid to see. Tilden beat Koželuh 50–17 on the 1931 tour. Even with greats such as
Ellsworth Vines,
Fred Perry, and
Don Budge as his opponents, all of them current or recent
world No. 1 players, it was often Tilden who ensured the box-office receipts—and who could still hold his own against the much younger players for a first set or even an occasional match. Tilden was ranked world No. 1 pro by Ray Bowers in 1931 and 1932 and Ellsworth Vines in 1933. Tilden thought he reached the apogee of his whole career in 1934 at 41 years old; nevertheless, that year he was dominated in the pro ranks by
Ellsworth Vines.
American Lawn Tennis reported that Vines had an edge of 11–9 in the first phase of their tour from January 10 through February 16 and that Vines led Tilden by 19 matches after the second phase of their tour, played from March 21 through May 17. Tilden had won 17 times for the entire year, per an Associated Press report, so a probable win–loss record at tour's end was 36–17 in Vines' favor. Both players then met at least 6 times during the rest of the year (Ray Bowers has listed 5 tournament matches and 1 one-night program), all lost by Tilden. In May 1931 he won the inaugural
U.S. National Indoor Professional Championships, held at the Penn Athletic Club, Philadelphia against Vincent Richards. Later in July that year Tilden won his first
U.S. Pro title, beating Vincent Richards in the final in straight sets at the Forest Hill Stadium in New York. Tilden also won the French Pro title in 1934. In 1935, he took his second US Pro title beating Kozeluh in the final. The same season he was beaten in the final of the
Pacific Southwest Indoor Professional Championships in November by
Lester Stoefen. By the late 1930s, Tilden was in his mid 40s and past his prime, but he was capable of playing excellent tennis in patches. Tilden lost easily to
Don Budge in the 1941 World Series. Budge said of Tilden "Bill could invariably manage to keep things close for a while. It was seldom, however, that he could extend me to the end, and I swamped him on the whole tour". In 1945, the 52-year-old Tilden and his long-time doubles partner
Vinnie Richards won the professional doubles championship—they had won the United States amateur title 27 years earlier in 1918. After playing the pro tournament circuit in 1946, the 53-year-old Tilden served a jail term. He returned to pro tennis briefly in 1948, playing a short series of matches against Wayne Sabin. Tilden's final farewell came in 1951. He faced George Lyttleton Rogers in a tour in April and May. Tilden lost in the quarterfinals to
Frank Kovacs at the Cleveland tournament in June 1951. Tilden was 58 years old. It had been 35 years earlier, in 1916, that he had made his singles debut at the US (Amateur) championships.
Davis Cup coach Tilden coached
Germany's tennis team in the 1937
Davis Cup. In the inter-zone finals, the U.S. team won after the deciding singles clash between
Gottfried von Cramm and
Don Budge, a match which has been called "The Greatest Tennis Match Ever Played". ==Place in sports history==