Weisweiler took over as manager of Borussia Mönchengladbach in 1964.
The club's most recent major title had been its win in the German cup in 1960, and it had found itself in the second division after the inception of the Bundesliga, finishing eighth in the year before he arrived.

Weisweiler found a team with some exciting young local talent, such as the 19-year-old Günter Netzer and Jupp Heynckes.
Also Bernd Rupp and Herbert Laumen were notable, they later played for the national team.
The next year Borussia, the average age of the players a mere 21.5, finished first in its division and gained promotion to the Bundesliga.

With the beginning of the new season another remarkable 19-year-old, Berti Vogts, was to join the team.
The first two years in the Bundesliga were learning years.
Despite the later addition of another talented player, Herbert Wimmer, Borussia finished in 13th and 8th place in the league.
In its third year the club came to the attention of a wider audience and finished third, despite losing Heynckes to Hannover 96.
The team, by now known for their attacking style, repeated that success the following year.
At the beginning of the 1969–70 season Borussia was even widely tipped as being the holders Bayern Munich's main rival for the Championship, as the defense had been strengthened with the arrival of international Ludwig Müller, and the attack boosted by the addition of Danish international Ulrik Le Fevre.
Most important, however, the younger talents, now including players like Horst Köppel, had reached sufficient maturity to hold their own on the highest level.
Decisive also was Weisweiler's ability to find and add further gifted young players.
This "youth culture" eventually gave Borussia the nickname they still carry today: the Foals.

Indeed, at the end of the year the team was crowned champion for the first time, and twelve months later the club from the small town became the first side in Bundesliga history to defend the league title.
This was secured with a 4–1 away win in Frankfurt, which enabled Borussia to fend off a late Bayern challenge on the last match day.

The team's first European Champions Cup participation had ended in the second round, when after two 1–1 draws with Everton, Borussia lost in the penalty shoot-out.
Their second challenge ended in heartbreak.
This time Helenio Herrera's catenaccio specialists Inter Milan, at the time one of Europe's most celebrated sides, visited the Bökelberg stadium.
During the first half of the match, with Borussia leading 2-1, Inter's Roberto Boninsegna was allegedly hit in the head by a soft drink can thrown from the stands, and had been stretchered off.
It is disputed that he had actually been struck, or if he had if it had truly caused him injury.
Borussia had obliterated Inter by a final score of 7–1.
Netzer later said his team had played so well they would have defeated any side in Europe by a huge margin, however Inter players said that when Boninsegna got stretchered off they essentially stopped playing.
The empty can was presented to the referee, and afterwards when Inter's officials complained, the governing authorities annulled the match and ordered it to be replayed on a neutral ground.
Inter won its home leg against Borussia 4–2, and the neutral match played in Berlin ended 0–0.
The annulled match has come to be called 'the Match of the Can', Inter went on to lose in the European Cup final to Ajax.

In the Bundesliga it was not a great year for the Foals.
Only three days after the initial triumph against Inter they defeated the surprise team of the season, Schalke 04, 7–0, but Bayern Munich won the title and Borussia finished third.
 Before the season Borussia had let Dietrich, Horst Köppel and Herbert Laumen go, and important parts of the team were crucially weakened, as new talents such as Rainer Bonhof and Dietmar Danner were not yet able to fill the gaps.

The 1972–73 season saw a further restructuring of the team.
This time experienced players such as Ulrik Le Fevre left the club, replaced by two young Danish forwards Henning Jensen and
Weisweiler took over as manager of Borussia Mönchengladbach in 1964. The club's most recent major title had been its win in the German cup in 1960, and it had found itself in the second division after the inception of the Bundesliga, finishing eighth in the year before he arrived.
Weisweiler found a team with some exciting young local talent, such as the 19-year-old Günter Netzer and Jupp Heynckes. Also Bernd Rupp and Herbert Laumen were notable, they later played for the national team. The next year Borussia, the average age of the players a mere 21.5, finished first in its division and gained promotion to the Bundesliga.
With the beginning of the new season another remarkable 19-year-old, Berti Vogts, was to join the team. The first two years in the Bundesliga were learning years. Despite the later addition of another talented player, Herbert Wimmer, Borussia finished in 13th and 8th place in the league. In its third year the club came to the attention of a wider audience and finished third, despite losing Heynckes to Hannover 96. The team, by now known for their attacking style, repeated that success the following year. At the beginning of the 1969–70 season Borussia was even widely tipped as being the holders Bayern Munich's main rival for the Championship, as the defense had been strengthened with the arrival of international Ludwig Müller, and the attack boosted by the addition of Danish international Ulrik Le Fevre. Most important, however, the younger talents, now including players like Horst Köppel, had reached sufficient maturity to hold their own on the highest level. Decisive also was Weisweiler's ability to find and add further gifted young players. This "youth culture" eventually gave Borussia the nickname they still carry today: the Foals.
Indeed, at the end of the year the team was crowned champion for the first time, and twelve months later the club from the small town became the first side in Bundesliga history to defend the league title. This was secured with a 4–1 away win in Frankfurt, which enabled Borussia to fend off a late Bayern challenge on the last match day.
The team's first European Champions Cup participation had ended in the second round, when after two 1–1 draws with Everton, Borussia lost in the penalty shoot-out. Their second challenge ended in heartbreak. This time Helenio Herrera's catenaccio specialists Inter Milan, at the time one of Europe's most celebrated sides, visited the Bökelberg stadium. During the first half of the match, with Borussia leading 2-1, Inter's Roberto Boninsegna was allegedly hit in the head by a soft drink can thrown from the stands, and had been stretchered off. It is disputed that he had actually been struck, or if he had if it had truly caused him injury. Borussia had obliterated Inter by a final score of 7–1. Netzer later said his team had played so well they would have defeated any side in Europe by a huge margin, however Inter players said that when Boninsegna got stretchered off they essentially stopped playing. The empty can was presented to the referee, and afterwards when Inter's officials complained, the governing authorities annulled the match and ordered it to be replayed on a neutral ground. Inter won its home leg against Borussia 4–2, and the neutral match played in Berlin ended 0–0. The annulled match has come to be called 'the Match of the Can', Inter went on to lose in the European Cup final to Ajax.
In the Bundesliga it was not a great year for the Foals. Only three days after the initial triumph against Inter they defeated the surprise team of the season, Schalke 04, 7–0, but Bayern Munich won the title and Borussia finished third.  Before the season Borussia had let Dietrich, Horst Köppel and Herbert Laumen go, and important parts of the team were crucially weakened, as new talents such as Rainer Bonhof and Dietmar Danner were not yet able to fill the gaps.
The 1972–73 season saw a further restructuring of the team. This time experienced players such as Ulrik Le Fevre left the club, replaced by two young Danish forwards Henning Jensen and 
Hennes Weisweiler