Born in Ihtiman, Baldzhiyski joined the youth academy of Levski Sofia and represented the club at all youth levels. He finally signed a full contract on 14 October 2008, at the age of 18. On 10 September 2009 Baldzhiyski started training with the first team. On the next day, he signed his new contract with Levski, with a better salary, connected him with the team until 2013. Baldzhiyski made his first appearance in the first team in a 2–0 win against Brestnik 1948 in a match of the Bulgarian Cup on 9 December 2009.
On 11 January 2010, Borislav was sent to Lokomotiv Mezdra on loan for six months. On 9 June 2010 he returned to Levski. In January 2011, Borislav was sent to Nesebar on loan for six months.
On 17 December 2016, Baldzhiyski signed with Cherno More for 1+1⁄2 years.[4] He made his debut against CSKA Sofia in a 0–2 home defeat on 19 February.[5] On 22 August 2017, Baldzhiyski's contract was terminated by mutual consent.[6]
Montana
On 24 August 2017, Baldzhiyski returned to Montana, signing a two-year contract.[7] However, he was released at the end of the 2017–18 season.[8]
Murder charges
Borislav Baldzhiyski was arrested for the murder of a 36-year-old man on August 6, 2013. If found guilty, he could be sentenced from 10 to 20 years in prison.[9] In September 2016, the Sofia city court declared him guilty of the lesser charge of manslaughter due to carelessness, imposing a four-year prison sentence.[10] On 4 July 2019 he was convicted guilty causing death by negligence, being conditionally sentenced to 2 years in prison with a maximum probation period of 5 years.[11]