The club's biggest success to date is the winning of the Bulgarian Cup in 1960 and finishing 5th in the Bulgarian first division during the same season. Septemvri is known for its strong youth academy, which over the years has developed numerous players for Bulgaria's elite clubs and the national team.
On November 5, 1944 the clubs Sportclub Sofia, Sokol and Vazrazhdane unite under the name of FC Septemvri Sofia. On March 26, 1945, the additional clubs of Botev (Konyovitsa), Ustrem (Zaharna fabrika), Pobeda (Krasna Polyana), and Svoboda (Tri kladentsi) merge into the club. In May 1948, the club, then playing in the 1st Sofia Division, is briefly merged with second-division CDV/Chavdar (Sofia) and the unified club wins the 1948 Bulgarian Championship by overcoming Levski Sofia in the final.
FC Septemvri's roots prior to merging with CSKA Sofia (see lower right corner)
Septemvri starts the 1948–49 season in the newly formed A Republican Football Group, but only six months later is separated from CDV (Chavdar) and removed from the division, with the current title given to CDNV, Chavdar's new name, which would ultimately become CSKA Sofia. At the end of the 1948–49 season, Septemvri is allowed to take part in a two-match play-off for entering first division against Marek Dupnitsa. After both matches end with a 2:0 win for each team, a third game is played in which Septemvri falls 1:0 and remains in second division.
From 1949 to 1969, Septemvri exists as an independent club, during which period it reaches the height of its success. In 1959, the club finishes first in the B PFG and is promoted to first division for the 1959–60 season. That same season, Septemvri finishes in 5th place and claims the Bulgarian Cup after a dramatic 4:3 win over Lokomotiv Sofia in extra time. The club's stay among the elite lasts only two years, as in 1961 it is relegated to the B PFG, where it remains until 1968.
In 1969, during another period of football reform in Bulgaria, Septemvri was again merged into CSKA Sofia. This unification continued for almost 20 years, until 1988, when the club became independent again and joined the V AFG. In 1993, Septemvri won a promotion to the B PFG. In 1998, the club became the champion of the B PFG and joined the elite for the first time since 1961. It finished in 16th place and was relegated again.
During the 2000–01 season, the club finished in 13th place in the B PFG and was relegated to the V AFG, where it remained until 2008. In March 2008, the club was heavily penalized after a scandalous match against FC Bansko, when coach Rumen Stoyanov ordered his players to leave the field, a serious offence according to Bulgarian Football Union regulations. With an executive decision, the BFU removed Septemvri from the V AFG and placed it in the A OFG, the Sofia Regional Football Group. Despite this setback, the club attained 1st place in the division in the 2008–09 season and qualified for a play-off match for entering the V AFG against FC Novi Iskar. After an emotional 0–0 in regular time, penalty kicks were in order to determine the team going forward. Septemvri lost the penalty shootout 5–4.
Merge with DIT academy and Pirin Razlog (2015–2017)
In 2015, Rumen Chandarov, owner of DIT Sport Academy, one of the best Bulgarian football academies in the last few years, announced that he is the new owner of Septemvri, with the goal of getting the young players to compete in the First Professional Football League of Bulgaria. The team merged with Conegliano German and started the 2015–16 season from V Group. Nikolay Mitov was appointed as a manager of the team. In the end of the 2015 it was decided that the team will give a bigger chance to their U19 players, so most of the players who joined in the season start left and only seven players left, but 18 players joined from the U19 team which was third in the Elite Youth Group by the end of 2015. Some media announced that Chandarov will stop financing the team also due to the fact that he started financing Botev Plovdiv, but Chandarov said that this is not true and the only reason to do this is to make youth players enter the men's football.
Septemvri could not avoid relegation in the next season, however, as they were relegated after losing in the relegation playoffs to FC Arda Kardzhali , 0-1. This ended their two year stay in the Bulgarian elite.
Back in the second tier after two seasons in the elite, Septemvri managed to maintain their good form and remained largely within the top three in the Second League, a strong candidate for promotion. The 2019-20 season was eventually not finished, due to the COVID-19 outbreak in Bulgaria. The last matches were played in early March. At that time, Septemvri was second in the league, three points behind CSKA 1948. This means that Septemvri will face the 13th placed team from the First League in a promotion playoff.
From 1944 to 1990 team main color is red with white or blue. From 1990 to 2010 team main color is purple, but in the period between 2001 and 2007 they used white with red colors. From 2011 team first kit is dark red.
Up to one non-EU national can be registered and given a squad number for the first team in the Second League. Those non-EU nationals with European ancestry can claim citizenship from the nation their ancestors came from. If a player does not have European ancestry he can claim Bulgarian citizenship after playing in Bulgaria for 5 years.