[3] A month later Alexandar made his debut for the Bulgaria Davis Cup team against Turkey,[4] losing the first match to Marsel İlhan, but claiming his maiden win over Altuğ Çelikbilek in the second.

In September he won his first ITF singles title at the Serbia F8 event in Sokobanja, defeating Filip Veger in the final.

Lazarov lost in the first qualifying round at the ATP Sofia Open in 2017 and 2018, but at the 2019 event the Bulgarian defeated Lukáš Lacko and Luca Vanni to guarantee himself a spot in the main draw for the first time.

The Bulgarian's good form continued in the following week at the M25 event in Telavi, where he didn't lose a set on his way to his fourth ITF singles title.

Lazarov finished his season with two consecutive ATP Challenger quarterfinals in Manama and in Antalya where he lost to the eventual champion Evgenii Tiurnev and reached a new career-high ranking of No.

Aleksandar continued his rise in the rankings during the summer after he won his fifth ITF title on home soil in Sofia as well as a final showing at the M25 event in Tbilisi the following week.

His best result to date came at the Rafa Nadal Open, where he made his way into the main draw and after five consecutive wins he reached his first semifinal on the ATP Challenger Tour as a qualifier.

[12] At the same tournament in the doubles competition, he scored another ATP main draw win with Alexander Donski before losing in the quarterfinals to top seeds Fabio Fognini and Simone Bolelli.

In February, Lazarov received a wildcard for the qualifying draw at the 2023 Dubai Tennis Championships, making his maiden appearance at the ATP 500 level.

In May, at the 2023 Upper Austria Open Lazarov tore the Achilles tendon in his left leg during his first round match against Sandro Kopp.