[4][5][6][7] He started to play football at Corvinul Hunedoara's youth center in 1973, making his debut for the senior team on 24 August 1977 under coach Ștefan Coidum in a Divizia A match which ended 2–2 with Argeș Pitești.

[6][7][4][12][14] After the 1989 Romanian Revolution, Klein went to play in Germany for Bayer Uerdingen, making his Bundesliga debut on 14 September 1990 when coach Horst Wohlers used him all the minutes in a 2–0 away loss in front of Karlsruher SC.

[17] Michael Klein played 89 matches and scored five goals at international level for Romania, making his debut on 9 September 1981 when coach Valentin Stănescu sent him on the field in the 49th minute in order to replace Aurel Beldeanu in a friendly which ended with a 2–1 loss against Bulgaria.

[1] He made seven appearances at the successful Euro 1984 qualifiers in which he scored one goal in a 2–0 win over Sweden, being used by coach Mircea Lucescu in all the minutes of the three matches from the final tournament as Romania did not pass the group stage.

[1] Michael Klein played six games at the Euro 1992 qualifiers and in the last one of them, he made his final appearance for the national team which took place on 13 November 1991 in a 1–0 victory against Switzerland.