An avid student of Aron Nimzowitsch theories, his play was renowned for its virtually impenetrable defence and patient manoeuvring, a technique that earned him the nickname “Iron Tigran”. Despite this, his capacity for dealing with tactical complications when the need arose prompted Boris Spassky to comment that: ”It is to Petrosian's advantage that his opponents never know when he is suddenly going to play like Mikhail Tal, and Robert James Fischer to observe that "He has an incredible tactical view, and a wonderful sense of the danger... No matter how much you think deep... He will 'smell' any kind of danger 20 moves before!" Petrosian’s pioneering use of the positional exchange sacrifice underscored both his positional and tactical grasp of the game. Moreover, he has two major opening systems named after him: the Petrosian Variation of the King's Indian Defence (1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 O-O 6.Be2 e5 7.d5) and the Petrosian System in the Queen's Indian Defence (1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.a3). He also advanced to the Fischer-Petrosian Candidates Match (1971) semifinals, but lost the opportunity to qualify to the 1972 championship.

National Championships: Petrosian first major win was the championship of Georgia in 1945 when he was 16. He won the 5th USSR Junior Championship in 1946 with a score of 14/15, won or came equal first in the championships of Armenia held in 1946, 1948, 1974, 1976 and 1980, won the Moscow championship in 1951; and shared first place with Vladimir Simagin and David Bronstein in the 1956 and 1968 Moscow Championships respectively. He gained his International Master title in the 1951 Soviet Championships, and went on to win the Soviet championship outright three times in 1959, 1961, and 1975, sharing the title with Lev Polugaevsky in 1969.

World championships: Petrosian won his Grandmaster title when he came equal second in the 1952 Interzonal tournament in Stockholm, which also qualified him for the 1953 Candidates tournament in Zurich. An eight time Candidate for the World Championship in 1953, 1956, 1959, 1962, 1971, 1974, 1977 and 1980, he won the Curacao Candidates Tournament of 1962 without losing a single game. The following year, he won the Petrosian-Botvinnik World Championship Match (1963) to become the 9th official World Chess Champion. He retained his title by winning the Petrosian-Spassky World Championship Match (1966), the first time since the Alekhine-Bogoljubov World Championship Rematch (1934) that the World Champion had succeeded in winning a title match. This feat was not repeated until Anatoly Karpov ’s success at the Karpov-Korchnoi World Championship Match (1978).

Team Play: Petrosian played in ten consecutive Soviet Olympiad teams from 1958 to 1978, winning nine team gold medals, one team silver medal, and six individual gold medals. His overall performance in Olympiad play was +78 =50 −1, the only loss being to Robert Huebner. He also played for the Soviet team in every European Team Championship from 1957 to 1983, winning eight team gold medals, and four board gold medals.

Classical Tournaments: Soon after becoming champion, he shared first place with Paul Keres in the first Piatagorsky Cup in Los Angeles in 1963. He won the tournaments at Biel and Lone Pine in 1976, the Keres Memorial in 1979, and took second place in Tilburg in 1981, half a point behind the winner Alexander Beliavsky. He was ranked among the top 20 players in the world until he died in 1984.

"Chess is a game by its form, an art by its content and a science by the difficulty of gaining mastery in it. Chess can convey as much happiness as a good book or work of music can. However, it is necessary to learn to play well and only afterwards will one experience real delight." - Tigran Petrosian