The 2009–10 season of Bayern Munich began on 1 July with their first training session, led by the team's new head coach Louis van Gaal.

[1] Bayern made several squad changes, signing Alexander Baumjohann, Edson Braafheid, Mario Gómez, Ivica Olić, Danijel Pranjić and Anatoliy Tymoshchuk.

Alexander Baumjohann was signed by his first club, Schalke,[6] and Bayern loaned Edson Braafheid to Celtic in a last minute deal before the end of the winter transfer period.

[7] The Reds did not buy any new players themselves, but gave professional contracts to Diego Contento and Mehmet Ekici from Bayern II.

Their choice fell on the Dutch Louis van Gaal, who had just led AZ Alkmaar to a championship in his home country.

Before Van Gaal's arrival, the club had already signed Mario Gómez for a Bundesliga record sum of €35 million, as well as Anatoliy Tymoshchuk, Ivica Olić and Alexander Baumjohann.

On the outgoing side, the loanee Massimo Oddo returned to Milan, Tim Borowski was sold to his former club Werder Bremen, Lúcio left for Inter Milan after many successful years with the Reds, and Zé Roberto signed with Hamburger SV when he could not agree with Bayern on a new contract.

While Van Gaal was not happy with the packed schedule, as he preferred to work with the team, Bayern played a mostly successful preseason, including several high wins against opponents from lower tiers.

They also managed to win in their own Audi Cup for which they had invited international premier clubs Milan, Manchester United, and Boca Juniors.

On the day prior to the first competitive game of the season, the cup match at Neckarelz, the coach announced his decisions.

Just before the next Bundesliga match, Bayern announced that they had signed Arjen Robben in a last minute transfer from Real Madrid.

FC Köln saw the Reds to the eighth place in the league, marking the worst start in decades, and the media already speculated about an even quicker sacking of Van Gaal than that of Klinsmann the previous season.

As Bordeaux already secured qualification to the knockout phase, many expected that they would not put all their effort into their next match against Juventus, and a win of the Italians would mean the end of Bayern's Champions League campaign this season.

The Reds won their last four league matches before the winter break, and also managed to win at Haifa while Bordeaux indeed defeated Juventus, meaning that Bayern and Juventus decided who qualified for the next round face to face in the final match of the group stage.

When David Trezeguet put Juventus in front in the 19th minute, prospects looked bleak for Bayern, but they managed to turn the game around and eventually won 4–1.

A draw at Cologne and a victory against SC Freiburg completed Bayern's streak of 19 undefeated games in the league.

On 9 March at Fiorentina, the club also reached the next round of the Champions League although their first loss after the winter break, 3–2, meant that they advanced only on the away goals rule.

Despite a loss at Eintracht Frankfurt on 20 March, Bayern stayed in first place, but that was of minor importance as the deciding weeks were yet to come.

The first game of their semi-final against Lyon was a heated affair with red cards on both sides, but Bayern emerged victorious.

Bayern had no post-season friendlies this year, but eleven players where internationals of teams that had qualified for the 2010 FIFA World Cup.

Arjen Robben and Mark van Bommel were part of the Dutch squad and seven players, Butt, Lahm, Badstuber, Schweinsteiger, Klose, Müller, and Gómez, were called up for Germany.

[9] Any sale of shares in FC Bayern München AG taking the total in outside hands to more than 30% of the stock will now require the approval of a 75% majority at the AGM.

Having defeated Rot-Weiß Oberhausen, Eintracht Frankfurt, and SpVgg Greuther Fürth in the following rounds, Bayern visited Schalke 04 in the semi-final on 24 March 2010.

McFit, a chain of fitness studios, had paid €1 million for the match in an action favoring the Ein Herz für Kinder foundation.

The McFit team was captained by Oliver Pocher and included other German celebrities like Johannes B. Kerner.

Also a few former professional footballers like Mario Basler, Ebbe Sand, and Thomas Häßler complemented the amateur squad.

Bayern arranged this friendly game to give Mark van Bommel, Luca Toni, and Martín Demichelis some practice after their injuries.