[14][18] During his period spent in Turkey, Nunweiller played four games in the 1968–69 European Cup where he helped Fenerbahçe eliminate the champion of England, Manchester City and in his second season spent at the club he was coached by Traian Ionescu and was teammate with Ilie Datcu, all of them previously working together at Dinamo, winning together the Turkish Super League title, a TSYD Cup in which he scored the only goal from the final against Beşiktaş, also being elected the best foreign player of the Turkish League 1969–70 season.

[1][8][14] Ion Nunweiller played 26 games at international level for Romania, making his debut on 26 October 1958 under coach Augustin Botescu in a friendly which ended with a 2–1 loss against Hungary.

[2][20] He played four games at the 1960 European Nations' Cup qualifiers as Romania eliminated Turkey in the round of 16, reaching the quarter-finals where they were defeated by Czechoslovakia, who advanced to the final tournament.

[4][21][22] After ending his playing career in 1972, Ion Nunweiller became the head coach of Dinamo București, managing to win the title in his first season, one of his players being his brother, Radu.

[11][21][25] In the following years he qualified Flacăra Moreni to the 1989–90 UEFA Cup, had an experience in Turkey at Bursaspor and obtained the first ever promotion to Divizia A of his hometown team Ceahlăul Piatra Neamț.

[24][28][29] After his death, his former Dinamo teammate, Cornel Dinu talked about him:"He was the creator of the symbol of The Red Dogs and the main pillar of resistance through which the great team was built from the beginning of the 60s.