The visitors came from one down as Jeremie Frimpong's early strike was cancelled out by goals from Julian Brandt, Julian Ryerson, Karim Adeyemi and Serhou Guirassy.

Alonso, who took Leverkusen to a league and cup double last year in his first full season in charge, announced his impending departure from the club on Friday, with Real Madrid the Spaniard's likely destination.

Leverkusen's title defence fizzled out with a 2-2 draw at Freiburg last Sunday, but the home fans were in a celebratory mood, one year after Alonso took them to a first league title in their 120-year history.

Before the game, Leverkusen celebrated Alonso's time at the club as fans chanted 'Danke Xabi' and held up placards with pictures of the Basque coach, but Dortmund were in no mood to celebrate.

The hosts dominated the opening period, pinning Dortmund in their own half. Only some spectacular saves from Dortmund goalkeeper Gregor Kobel, who made seven stops before half-time alone, kept Leverkusen at bay.

Leverkusen's pressure finally told with 31 minutes gone when Florian Wirtz waltzed through the penalty area, attracted three defenders before laying the ball off to Frimpong who curled a shot into the top corner.

Dortmund had barely left their own half but the goal shook them to life. The visitors equalised two minutes later, Adeyemi cutting the ball back for Brandt to hammer home.

Brandt engineered Dortmund's second two minutes before the break, winning a ball near the sideline and finding a cross to Pascal Gross, who swivelled and teed up Ryerson to drive a low shot into the net.

Both Adeyemi and Guirassy, who each scored braces in last week's 4-0 thumping of Wolfsburg, got on the scoresheet in the space of four second-half minutes.

Guirassy now has 33 goals from 44 games in his first season in Dortmund.

Wirtz, who has been linked with a summer departure, laid on a late consolation goal for Jonas Hofmann in stoppage time.

Alonso will coach Leverkusen one more time, in next week's game at Mainz, but Leverkusen cannot finish any higher or lower than second.

Dortmund now sit one point behind fourth-placed Freiburg, with one more game to play.

Later on Sunday, Eintracht Frankfurt can shore up a Champions League spot when they host St Pauli, while German Cup finalists Stuttgart play at home to Augsburg.