Edwin Tsai played men's singles and doubles at Wimbledon three years in a row from 1952-54. He also competed in mixed doubles twice in 1953 and 1954. In his maiden appearance at SW19, he fought all the way to the fifth set before he bowed out to 20-year-old Robert Haillet, who had just made his Davis Cup debut for France earlier that year. In 1953, he was victorious in the opening round against Headley Baxter, who went on to captain the British Davis Cup team in the 1960s and 70s. In the second round, however, he was stopped by American Budge Patty, the 1950 French Open and Wimbledon champion, and ranked No. 1 in the world that year by John Olliff of The Daily Telegraph. The following year, Tsai also managed to reach the second round after beating Iran's Matthew Mohtadi but exited at the hands of Australian Davis Cupper Rex Hartwig, who was ranked No. 5 in the world in 1954 by Lance Tingay of The Daily Telegraph.
Tsai also competed in the men's doubles at Wimbledon twice, playing alongside fellow HKTA Hall of Famer, Ip Koon Hung. In 1952, they reached the second round before the Aussie-American duo of Ian Ayre and Ham Richardson halted their progress. Richardson went on to win back-to-back NCAA singles titles the following two years, played on two Davis Cup winning teams, and ranked as high as No. 3 in the world in 1956 by Lance Tingay of The Daily Telegraph. Then in 1954, Tsai and Ip teamed up to beat Pierre Geelhand de Merxem of Belgium and Harry Hopman of Australia en route to round two before they were bounced by No. 3 seed Lew Hoad and Ken Rosewall, who paired up to win three of the four Grand Slam doubles titles the previous year in 1953. Hoad and Rosewall both went on attain the world No. 1 ranking in singles in 1956 and 1960, respectively.
In mixed doubles, he teamed up with Bermuda's Heather Brewer to reach the last sixteen in 1953 and made the third round the following year together with American Kay Hubbell.
Tsai competed in a number of tournaments in the UK around the time of Wimbledon, such as the Queens Club Tennis Tournament and Surrey Championships. He was also a finalist at the Priory Club in 1953 and Ulster Championships in 1954.
Locally, from 1955-60, Tsai reached six consecutive men's singles finals at the Hong Kong National Grasscourt Championships, a span during which he finished runner-up to Ip Koon Hung five times and once against KC Dao. In addition, he competed in nine men's doubles finals, winning in 1950, 1952, 1954-56, and 1962, and finished runner-up in 1957-58 and 1965. In mixed doubles, he lifted titles in 1953, 1955, and 1957.
Moreover, his prowess also extended to the hardcourts of the CRC Open where he triumphed in men's singles in 1955 and won the men's doubles a record eleven times in 1949, 1952-56, 1958-61, and 1963.
In 1973, Tsai served as Executive Vice-President of the Hong Kong Lawn Tennis Association.