Asparuhov began his senior career at Levski Sofia in the end of 1959–60 season at the age of 17. He made his debut on 5 June 1960 in a 1–0 home loss against Lokomotiv Sofia, coming on as a second-half substitute.^[5] His first senior goal came during the following campaign when he scored in a 1–1 away draw against Botev Plovdiv on 28 September 1960.

In January 1962, Asparuhov joined Botev Plovdiv where he won 1961–62 Bulgarian Cup a few months later. On 13 September 1962, he marked his European debut away at Steaua București with two goals, but Botev lost the game 3–2 in their preliminary round first leg tie of 1962–63 Cup Winners' Cup. A week later, in the second leg of Botev's European tie against Steaua, Asparuhov scored his first-ever hat-trick in a resounding 5–1 home victory. He also scored in a 4–0 away win over Shamrock Rovers on 24 October 1962 and became a top scorer of the tournament with 6 goals.

In October 1963, Asparuhov returned to Levski Sofia.^[6]

Widely regarded as Levski's greatest ever player, Asparuhov played over 230 games for the club, winning three Bulgarian League titles and three Bulgarian Cups. During his time at the club he won the Bulgarian footballer of the year and Bulgarian sportsperson of the year in 1965.

Asparuhov is Levski's third all-time leading goal scorer (153). In 1964–65 season he became the league's top scorer with 27 goals in 29 matches.

Some of the top European clubs at the time sought his services. In the 1965–66 European Cup, Levski played Benfica, with Eusébio in the squad of the Portuguese. When Benfica eliminated Levski in a tight tie, and Gundi having netted 3 of Levski's 4 goals across both legs, Europe began to view him with interest. In fact, he was the first foreign player to have scored two goals at Benfica's stadium. Asparuhov was wanted by Benfica themselves.

In the history of Bulgarian football, it is often claimed that in 1967 Georgi Asparuhov was invited to join AC Milan, despite the fact that at the time the transfer of leading Bulgarian players to Western clubs was highly restricted and subject to state control.^[7] The alleged interest is associated with the renowned “rossoneri” coach Nereo Rocco. Asparuhov is also frequently credited with the following emblematic response, which has become part of football folklore:

"Tell them there is a country named Bulgaria. In that country there is a team called Levski, they might not have heard of it. But I was born in this team and I will die there."^[8]

Despite the widespread circulation of this story, it should be approached with a degree of caution given the specific historical context. Following Italy’s disappointing performances at the 1962 and 1966 FIFA World Cups, the Italian Football Federation introduced restrictions on the recruitment of foreign players by Serie A clubs, which remained in place until 1980.^[9][10] The rule did not apply to foreign players who already had professional contracts with Italian clubs, nor to the so-called oriundi—players of Italian descent born abroad who could obtain Italian citizenship. This means that by 1967 there was no clear regulatory pathway that would have allowed the registration of a Bulgarian player in the Italian league, even if there had been genuine interest from a coach or club management.

Scores and results list Bulgaria's goal tally first.

Georgi Asparuhov: International Goals^[25]

#	Date	Venue	Opponent	Score	Result	Competition
1.	7 November 1962	Vasil Levski National Stadium, Sofia	Portugal	1–1	3–1	1964 European Nations' Cup Qualification
2.				2–1
3.	6 January 1963	20 August 1955 Stadium, Belouizdad	Algeria	1–0	1–2	Friendly
4.	23 January 1963	Stadio Olimpico, Rome	Portugal	1–0	1–0	1964 European Nations' Cup Qualification
5.	13 June 1965	Vasil Levski National Stadium, Sofia	Israel	3–0	4–0	1966 World Cup Qualification
6.	26 September 1965	Vasil Levski National Stadium, Sofia	Belgium	2–0	3–0	1966 World Cup Qualification
7.	21 November 1965	Ramat Gan Stadium, Ramat Gan	Israel	2–1	2–1	1966 World Cup Qualification
8.	29 December 1965	Stadio Comunale, Florence	Belgium	1–0	2–1	1966 World Cup Qualification
9.				2–0
10.	14 June 1966	Stadio Comunale, Bologna	Italy	1–2	1–6	Friendly
11.	20 July 1966	Old Trafford, Manchester	Hungary	1–0	1–3	1966 World Cup
12.	12 November 1967	Vasil Levski National Stadium, Sofia	Sweden	3–0	3–0	Euro 1968 Qualification
13.	27 October 1968	Vasil Levski National Stadium, Sofia	Netherlands	2–0	2–0	1970 World Cup Qualification
14.	11 December 1968	Wembley, London	England	1–0	1–1	Friendly
15.	23 April 1969	Vasil Levski National Stadium, Sofia	Luxembourg	1–0	2–1	1970 World Cup Qualification
16.				2–0
17.	15 June 1969	Vasil Levski National Stadium, Sofia	Poland	4–1	4–1	1970 World Cup Qualification
18.	24 February 1970	Estadio Nacional del Perú, Lima	Peru	2–3	3–5	Friendly

Botev Plovdiv

• Bulgarian Cup: 1961–62

Levski Sofia

• Bulgarian League (3): 1964–65, 1967–68, 1969–70
• Bulgarian Cup (3): 1966–67, 1969–70, 1970–71

• Bulgarian League top scorer: 1964–65 (27 goals)
• UEFA Cup Winners' Cup top scorer: 1962–63 (6 goals)
• Bulgarian sportsperson of the year: 1965
• Bulgarian footballer of the year: 1965
• Best Bulgarian footballer of the 20th century
• 1965 Ballon d'Or: 8th place
• 1966 Ballon d'Or: 14th place
• 1968 Ballon d'Or: 14th place
• FUWO European Team of the Season: 1968^[26]
• Stara planina order: 2014
• Holder of an Order of Labour
• Deserved Master of Sports
• Holder of the Fairplay prize /posthumously/: 1999
• IFFHS Top 100 Best European Players of the 20th Century: 40th place^[3]

Bulgaria

• UEFA Euro 1968: 5th place