Blaszczykowski's side, coached by Klopp, won 5-4 in front of 82,000 fans at a packed Westfalenstadion.
Former Borussia Dortmund coach Jurgen Klopp said his return to the club's coaching bench on Saturday for a memorable match was “like a high school reunion” nine years after his last match as the club's manager.
Dortmund bid farewell to veterans Jakub Blaszczykowski and Lukasz Piszczek, who each took charge of a team that included several club legends as well as current coach Nuri Sahin.
Blaszczykowski's side, coached by Klopp, won 5-4 in front of 82,000 fans at a packed Westfalenstadion.
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“It was like a high school reunion,” Klopp told Sky Germany, adding: “This is what I've always dreamed of: for us to meet again in life and just have a good time together.”
“It's like coming home. So many great memories. It's nice to see the fans again.”
Klopp spent seven years as manager of Borussia Dortmund, winning two Bundesliga titles, one DFB Cup and leading the team to the 2013 Champions League final at Wembley Stadium, where they lost to arch-rivals Bayern Munich.
Klopp, who stepped down as Liverpool manager at the end of last season citing fatigue, has yet to return to coaching, saying in July: “It's over for me as a manager today.”
The coach poked fun at the ageing players, saying: “We had a lot of extra weight in attack, midfield and defence today.”
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Dortmund also said goodbye to defender Mats Hummels, who left the club in the summer and joined Serie A side Roma.
Hummels, who made 508 appearances for Dortmund, was one of the few active players to feature.
He later said: “It's a mixture of joy and sadness.
“I spent most of my football life here.”