As a member of the
1967 Thomas Cup squad, Hartono won all of his matches, but
Indonesia was beaten by
Malaysia in a highly controversial final in which play was suspended due to the unruly crowd. Both teams were later offered a chance to resume their clash in New Zealand but Indonesia declined, thus handing Malaysia the cup. A year later, on his first try at the
All England Championships, the 18-year-old Hartono became the youngest ever champion of the tournament, beating
Tan Aik Huang from Malaysia who had been the winner two years earlier. From then on, he dominated the event like very few had before, winning seven titles consecutively from 1968 to 1974. Hartono, however, came back the following year to win his eighth title against his compatriot
Liem Swie King thus becoming the most successful men’s singles player in the history of the tournament. He attempted another comeback in 1981, but lost in the semi-finals to
Prakash Padukone in a three sets battle, 15–10, 7–15, 8–15. Besides his All England success, Hartono won many international open titles throughout his career. In 1969, he won the
Canadian and the
US Open titles after defeating
Sture Johnsson and his compatriot
Muljadi in the respective finals. In the same year, he also won both the
Singapore Open men's singles and doubles titles. He defeated Muljadi in the singles final and partnered with Indratno to beat Lee Wah Chin and Yeo Ah Seng in the doubles final. In 1971, he won his second Canadian Open title and clinched his first
Denmark Open title after defeating
Ippei Kojima on both occasions. He also competed in the Western Indian Championship that year and won a hat trick of titles, beating Muljadi in the men's singles final, partnered with
Indra Gunawan to beat Muljadi and Sumiratta in the men's doubles final and partnered with Rafia Latif to beat
Indra Gunawan and Sunila Ape in the mixed doubles final. In 1973 and 1975, Hartono won his second and third Denmark Open titles after beating
Flemming Delfs and Svend Pri respectively. In 1981, he would win his maiden
Japan Open title after beating his compatriot
Lius Pongoh in the final. Hartono also had some success in major games. At the
1970 Asian Games held in Bangkok, he won gold in the men's team event and two bronze in the men's doubles and mixed doubles events. In 1971, he would win another gold at the
Asian Championships where Indonesia defeated Malaysia in the men's team final. In the
1972 Munich Games in which badminton was presented as a demonstration sport, Hartono won the men’s singles event, after beating
Jamie Paulson of Canada in the first round, Sture Johnsson of Sweden in the semi-finals, and Svend Pri of Denmark in the final. In his attempt to win an 'official' world championships, Hartono participated in the
1980 IBF World Championships held in Jakarta and managed to reach the final where he would meet his successor Liem Swie King. In a final that lacked intensity, Hartono prevailed in two straight games with the score of 15–9, 15–9. Since his debut in 1967, Hartono remained active in the Thomas Cup competition and continued to play for his country at the event from 1970 to 1982. The
1970,
1973,
1976, and
1979 Thomas Cup would turn out to be a resounding success for Hartono and his team, with Indonesia sweeping four straight titles. At the
1982 Thomas Cup Finals, the aging Hartono once again answered the call of his nation but his play was not on par with his previous performances and he was not able to help his team to prevent China from winning their first ever Thomas Cup title. After the competition, Hartono announced his retirement, saying "I believe I have to retire now... Actually, I was already retired. But this was the Thomas Cup and my country needed me and because I live in Indonesia and I love Indonesia, I must do what they ask." ==Post-retirement==