The company highlighted that Debenhams has six million beauty shoppers and 1.4 million Beauty Club members.
Boohoo said: “The group intends to rebuild and relaunch the Debenhams platform, helping further the group’s stated ambition to lead the fashion e-commerce market, and grow into new categories including beauty, sport and homeware.”
Boohoo shareholders appeared to welcome the deal, with shares up 4% in early trading on Monday.
However, Shore Capital retail analyst Greg Lawless warned that an online-only operation could hit Debenhams’ beauty sales.
He said: “The big question in beauty is whether the big beauty brands – Clinique and Channel – will remain with Boohoo longer term.