Short answer when did the Williams sisters turn pro: Venus and Serena turned professional in 1994 and 1995, respectively. They went on to become two of the most successful tennis players ever, with a combined 30 Grand Slam singles titles between them., Serena Williams became a professional tennis player in 1995, just after her 14th birthday – her first professional event was in October 1995 (her birthday is in September) at the Bell Challenge in Quebec., Serena Williams became pro in 1995. She was at No. 99 in the global rankings two years later, up from No. 304 just a year earlier. She graduated from high school a year later and signed a $12 million shoe deal with Puma almost immediately., Williams did not play another professional match until 1997, but by the end of that year she rose to number 99 in the world rankings. In 1998, Williams’s ranking rose to number 20 and she surpassed Monica Seles to become the fastest player to record five victories against Top 10 players., Serena Williams is a retired professional tennis player. She won 23 Grand Slam singles titles and is considered by many to be the greatest female tennis player of all time. Did Serena Williams make an appearance in the Super Bowl Half-time show? Indeed, she did., Serena turned professional in 1995 at the age of 14. In 1999, she won her first Grand Slam singles title at the US Open, defeating Martina Hingis. This victory established her as a formidable force in women’s tennis. The early 2000s saw Serena ascend to the top of the sport..