Hrubesch played in small clubs until the age of 24 when he was signed by Rot-Weiss Essen. There he played well enough that in 1978 Hamburger SV bought him. At Hamburg he blossomed into one of the most productive forwards of the Bundesliga and was soon called up for the West German national team. Hrubesch formed an attacking partnership with fellow HSV player Manfred Kaltz, a right wingback whose crosses Hrubesch often headed in, or headed to teammates to provide them with scoring chances. Hrubesch won the West German championship three times with Hamburg, in 1979, 1982 and 1983; and his team finished second in the league standings twice, in 1980 and 1982. In all, he scored 96 goals in 159 matches for the club. Hrubesch won the European Cup in 1983, captaining the team to a 1–0 win against favourites Juventus in the final in Athens. Three years earlier he had been on the team that lost the 1980 European Cup Final against Nottingham Forest, however he was injured shortly before the game and could only feature as a half time substitute. Hamburg reached one other major European final while Hrubesch was on the team, losing the 1982 UEFA Cup final against IFK Göteborg. Hrubesch left Hamburg after the 1983 season to play for Belgian club Standard Liège. After two years he returned to the Bundesliga to play for Borussia Dortmund, appearing in about half the club's games during his one season there. Over the course of his entire career he scored 136 goals in 224 games in the Bundesliga.
West Germany's match-winning hero in the UEFA Euro 1980 Final in Rome against Belgium, Hrubesch scored two goals, the second a trademark bullet header, in the 89th minute. It was a day of redemption for the big Hamburger SV centre forward who a few weeks earlier had hobbled around the field with an ankle injury as his club lost the European Champion Clubs' Cup final to Nottingham Forest FC. A latecomer to the international scene, Hrubesch had only been called into the West Germany squad after Klaus Fischer broke his leg, and the game against Belgium was only his fifth international appearance. He would play for West Germany 21 times, scoring 6 goals, his last match being the losing 1982 FIFA World Cup final against Italy. Hrubesch is also famous for having scored the winning penalty which defeated France in the 1982 FIFA World Cup semi-final, after an epic game which was tied 3–3 after extra-time. Minutes earlier, in the second extra-time period with France leading 3–2, it was Hrubesch who headed a cross from the left wing to Klaus Fischer, enabling his spectacular overhead kick equalizer. Irish television commentator Jimmy Magee during the shoot-out coined the nickname that made Hrubesch best known in the English-speaking world: "The man they call 'The Monster'."
Hrubesch started his coaching career with Rot-Weiss Essen He was there between 1 July 1986 and 14 September 1987. His first match was a 2–0 loss against Rot-Weiß Oberhausen on 25 July 1986. He had won two of nine league matches and a first round exit from the cup before leaving the club. His final match was a 3–1 loss to Rot-Weiß Oberhausen on 13 September 1987. He won 16 of his 47 league matches. Hrubesch then took over VfL Wolfsburg for the 1988–89 season. In the cup, he had a draw and a loss. This includes a 1–1 draw and a 6–1 loss against to Eintracht Frankfurt. Hrubesch then took over Swarovski Tirol from 1 January 1992 to 30 June 1992. His first match was a 2–0 win against Austria Salzburg. Hrubesch took over at Hansa Rostock between 4 January 1993 and 26 June 1993. His first match was a 3–0 loss to Waldhof Mannheim on 6 February 1993. Hrubesch took over as head coach of Dynamo Dresden on 22 November 1994 and was there until 1 March 1995. He failed to win any of his five matches. His first match was a 1–1 draw against Karlsruher SC on 26 November 1994. Dynamo Dresden also lost a 2–1 to Bayern Munich, 1–1 draw against Bayer Leverkusen, 1–0 loss to Werder Bremen, and a 2–0 loss to VfL Bochum. Hrubesch was head coach of Austria Wien for the 1995–96 season. His first match was a 4–0 win against Vorwärts Steyr on 2 August 1995. Hrubesch was head coach of Samsunspor for the 1997–98 season. Samsunspor finished second in Group 6 of the UEFA Intertoto Cup, three points behind Hamburger SV. Their record was three wins and a loss. In the league, they finished with a record of 14 wins, seven draws, and 13 losses in 34 matches.