The branch in King William Street was closed for around a month while the work was carried out, although customers were able to contact the team by phone or visit Hays Travel's nearby Preston Fishergate branch during the closure.
The works form part of Hays's multi-million-pound programme to modernise its retail network, with a focus on "improving energy efficiency" and enhancing the customer experience.
Dame Irene Hays and Chief Operating Officer Jonathon Woodall-Johnston joined the team to cut the ribbon, with Branch Manager Stephanie Rowley describing the reopening as "one of the proudest days" of her career.
"It was brilliant to welcome Dame Irene and Jonathon to our fantastic new shop," she said. "Their support means so much to the team. We are all over the moon with the refurbishment and we can't wait to show it off to our customers."
Woodall-Johnston added: "It was a pleasure to visit Stephanie and her team in Blackburn, who continue to do an outstanding job supporting their local community.
"A key feature of this branch is our new foreign exchange concept, which places our award-winning travel money service front and centre, making it even more accessible and convenient for customers."
He added: "We remain committed to investing in our retail estate and it is always fantastic to see the results of these transformations following a refit."
