Aliaksandra Sasnovich started playing at age 9, introduced to tennis by her father, though she had practiced Taekwondo for a couple of years when she was younger.
She played the first event of her career at 2009 ITF Minsk 2, and made her WTA qualifying debut at 2013 Brussels. In 2014, she made WTA main draw debut at US Open and reached the second-round (as a qualifier, l. eventual R-Up Wozniacki). That year she won the 11th and most recent singles title on ITF Circuit.
The Belarusian ended 2015 season at No.103. That year she reached her first WTA final, at Seoul (as a qualifier, l. Begu) being one of four qualifiers to reach a WTA final in 2015. Sasnovich made her Top 100 debut on September 8.
Her 2016 season was highlighted by the quarter-finals run at Tokyo [PPO]: there, she won three rounds of qualifying before defeating Wickmayer and No.6 Karolina Pliskova before losing to eventual finalist Osaka.
Sasnovich posted career-best finish in 2017 at No.87, completing the first Top 100 finish of her career. Season highlights included the semifinals run in Biel and a quarter-finals appearance at Moscow. She played all three ties during Belarus’ run to its first Fed Cup final and posted a 5-1 record, including the win over No.13 Stephens in final.
In 2018, Sasnovich completed her first top-30 season at No.30. She opened the campaign reaching the second career WTA final and the first at a Premier tournament at Brisbane, as a qualifier, beating No.11 Mladenovic and No.16 Sevastova before losing to No.6 Svitolina). At Australian Open, she advanced to the third round of a major for the first time (l. Garcia). Afterward, she broke into Top 50 for the first time at No.46 on January 29.
She won back-to-back matches at Premier Mandatory level for the first time to reach the third round in Indian Wells (l. Wozniacki) before moving to the second round in Miami (l. Pavlyuchenkova).
She failed to win back-to-back matches during the clay season that culminated with a second-round showing at Roland Garros (l. Bertens). On grass, her only tour-level victories came at Wimbledon where she collected the first Grand Slam fourth round (l. Ostapenko). In the opening match, she upset No.8 Kvitova to score the second-best win by ranking in her career.
She made the semifinals at Moscow River Cup (l. eventual champion Danilovic) and posted a round-16 finish as a qualifier in New Haven (l. Garcia) before the Us Open. In New York, she claimed the best result in the tournament losing to eventual champion Osaka in the third round. After the final major of the season, she reached her career high ranking at No.30 on September 10.
During the Asian swing, she made the second round in Wuhan (l. Puig) and Beijing (l. Karolina Pliskova) and fell in the first round in Tokyo (l. Pavlyuchenkova). In her last tournament of the season, she defeated Buzarnescu in straight sets in the first round for the second consecutive tournament and upset No.10 Bertens in the second round scoring the third top-10 victory of her career after she beat No.6 Pliskova at 2016 Tokyo [PPO] and No.7 Kvitova at 2018 Wimbledon. She won back-to-back main draw matches for the first time since the US Open and the seventh time this year, losing to Konta in the quarterfinals.