Georgiev was born in Sofia. He is a product of the Slavia Sofia youth academy. He signed a professional contract in June 1999 and then made his first team debut under Miroslav Mironov' management three months later, on 17 October, in a 3–1 home win over Pirin Blagoevgrad. Georgiev's first goal came on 27 November 1999, when he scored a last-minute against Beroe Stara Zagora to secure a 1–1 away draw. On 11 March 2000, he netted Slavia's only goal in their league loss, a 2–1 defeat against Velbazhd Kyustendil. He then scored in Slavia's 3–2 win against Botev Plovdiv on 22 April, taking his tally for the season to 3 goals.
On 27 September 2003, Blago scored his first-ever hat-trick in his career, scoring four in a 5–2 away win over Chernomorets Burgas. After scoring his 17th league goal in the final game of the 2003–04 season, a 2–0 win against Naftex Burgas, he ended the campaign in joint second place with Stoyko Sakaliev in the race for the Bulgarian A PFG golden boot.
During his six years at Slavia Stadium, he scored 46 league goals in 172 matches.
On 13 January 2006, Deportivo Alavés confirmed Georgiev has joined on loan until the end of the season. He made his La Liga debut a week later, during Alaves's 2–0 loss against Barcelona at Camp Nou. He spent most of his time with Alaves on the bench. Blago returned to Bulgaria at the end of the season having made 10 appearances in Alaves's unsuccessful battle against relegation.
On 14 June 2006, Serbian side Red Star Belgrade signed Georgiev on a season-long loan deal.
On 28 May 2007, Georgiev joined Bundesliga side MSV Duisburg on loan until the end of the 2007–08 season. On 14 March 2008, he scored his first goal in a 2–1 loss against Schalke 04. On 4 May Blago scored a last-minute winning goal for 3–2 over Bayer 04 Leverkusen. During the season, he earned 31 appearances.
On 6 January 2009, Georgiev signed a four-year contract with Russian side Terek Grozny for 1.5 million Euros. He made his Russian Premier League debut on the opening day of the 2009 season, on 15 March, in a 1–0 home win over Spartak Nalchik. Georgiev's first goal came on 19 July, when he scored in a 3–2 home win against Zenit Saint Petersburg.
On the eve of the 2010 season, Georgiev was selected by manager Anatoly Baidachny, as the replacement captain after Timur Dzhabrailov's retirement. On 10 May 2010, he scored the opening goal of the league game against CSKA Moscow which Terek lost 1–4. Three days later, Blago provided two assists in a 2–0 home victory over Saturn Ramenskoye.
Georgiev scored his first league goal of the 2011 season and the winner against Anzhi Makhachkala, in a 1–0 victory on 20 May. On 13 August, he scored his second goal of the season, in a 6–2 defeat at Dynamo Moscow. On 5 November, in a 2–0 home victory over Krasnodar, Blago assisted Musawengosi Mguni for the second goal. On 28 December 2011, few days after his 30th birthday, he was reported to have become a target for Lokomotiv Moscow.
On 4 November 2012, Georgiev marked his 100th Russian Premier League game by scoring a penalty in a 3–1 loss against Anzhi Makhachkala.
Georgiev signed with Amkar Perm on 19 December 2012 on a three-year deal.
On 15 August 2014, Georgiev joined Rubin Kazan, signing a two-year deal. Following his transfer he took the number 77 shirt. He made his debut two days later, playing the full 90 minutes in a 1–1 home draw against Lokomotiv Moscow. His first league goal for Rubin gave them a 2–1 win over Torpedo Moscow on 29 September.
All stats correct as of 5 March 2017.
A Bulgaria international, Blagoy Georgiev was also previously a member of the country's under-21 team. He has been capped 50 times and scored 5 goals for Bulgaria. On 11 October 2011, he announced his retirement from Bulgarian national team. In September 2012, it was revealed that Georgiev may consider returning to the national team, but he is yet to add to his 50 caps for the "lions".Red Star Belgrade
Serbian SuperLiga: 2006–07
Serbian Cup: 2006–07
Georgiev is a devout Christian and has a number of faith-related tattoos.
Georgiev previously had a fling with singer Liana and was formerly in a long-term relationship with Hristina Vitanova (with whom he has two children). Georgiev is currently engaged to Russian dancer Esmer Omerova.