The former Spain international announced last week that he will leave the Bundesliga club at the end of the current campaign with Real Madrid his likely destination.
Even though Leverkusen fell to a 4-2 defeat against Borussia Dortmund, Alonso soaked in all the adulation from the fans at the BayArena.
Alonso is seen as a cult hero after leading Leverkusen to their first ever Bundesliga title last season in their 120-year history, going unbeaten throughout the entire campaign.
Speaking to DAZN, the Spanish mentor wanted to stay in the moment: "We will see in the future. Not too long, but we need to wait. Today is about our club, our players.
"For me it's the end of a super era in my life and I want to enjoy it, and afterwards we'll see.
"I was emotional and this club will stay in my heart forever."
Alonso took over in October 2022 with Leverkusen near the bottom of the table, lifting the club to a sixth-place finish before delivering the league trophy the following season.
The 43-year-old was presented with a 'Xabi Alonso Allee' street sign by club CEO Fernando Carro before Sunday's match.
He added: "I'll get it in my office, wherever it is, and I'll try and explain it to people in some years. It's a very meaningful thing for me, because it's from the fans, from the people, and it means even more.
"I remember it as one of the greatest times of my life."
Alonso's final game in charge of Leverkusen will be away to Mainz next Saturday.
Rodrygo's future at Real Madrid has been thrown into serious doubt, with reports in Spain claiming the Brazilian winger is so frustrated with his situation that he no longer wants to play for the club.
Bayer Leverkusen are reportedly closing in on Como's Cesc Fabregas as their top choice to replace outgoing head coach Xabi Alonso, who will depart at the end of the 2024-25 season.
Borussia Dortmund staged a powerful comeback in Leverkusen on Sunday, overturning a first-half deficit to claim a 4–2 victory and keep their hopes of a top-four Bundesliga finish alive heading into the final weekend of the season.
Bayern Munich celebrated their Bundesliga title win in style with a comfortable 2-0 win over Borussia Monchengladbach.
