Lengyel gained the title of International Master in 1962 and became a Grandmaster in 1964.
Lengyel played for Hungary in six Olympiads between 1960 and 1970. His most notable results were:
15th Chess Olympiad 1962 Varna - Lengyel scored 8½/12 receiving an individual bronze medal, and Hungary finished 5th of 37 teams.
17th Chess Olympiad 1966 Havana - Lengyel scored 4/10 and Hungary finished 3rd of 52 teams, receiving bronze medals
19th Chess Olympiad 1970 Siegen - Lengyel scored 5½/12 and Hungary finished 2nd of 60 teams, receiving silver medals
His overall Olympiad record was 41 points from 70 games.
Lengyel also played in the European Team Chess Championship three times between 1961 and 1970. His results were as follows:
2nd European Team Championship 1961 Oberhausen - Lengyel scored 5½/10 and Hungary finished 3rd receiving bronze medals.
3rd European Team Championship 1965 Hamburg - Lengyel scored 5½/10 receiving an individual bronze medal. Hungary also finished 3rd for team bronze.
4th European Team Championship 1970 Kapfenberg - Lengyel scored 3½/7. Hungary finished 2nd receiving silver medals.
Some notable results:
1962 Hungarian Championship (Budapest) 1st= (lost to Lajos Portisch in a playoff)
1963 Enschede Zonal 2nd= (with Klaus Darga, behind Svetozar Gligoric)
1964 Hungarian Championship (Budapest) 3rd= (behind Portisch)
1964 Málaga 2nd= 7½/11 (with Portisch, winner Arturo Pomar 8½)4
1966 Polanica Zdroj Rubinstein Memorial 2nd= 9/14 (with Heinz Liebert, behind Vasily Smyslov 11)5
1968 Solingen 1st (ahead of Bruno Parma, Ludek Pachman, Laszlo Szabo and Jan Hein Donner)
1972 Bari 1st
1972-73 Reggio Emilia 1st= 7/11 (with Luben Popov)6
1977 Budapest 1st
1977 Virovitica 1st
1977-78 Gausdal 1st
1980 Val Thorens 1st
1982 Val Thorens 1st= (with Miodrag Todorcevic)
Lengyel also played in the 1964 Amsterdam Interzonal, a preliminary round of the World Chess Championship, achieving 12th place with 13/23 (the winner was Smyslov with 17)[
At his peak, he was regarded as a strong grandmaster, competing for his nation at the top level and winning medals. He died in Budapest in 2014.
Lengyel had wins against former World Champion Mikhail Botvinnik.