The firm, which sells own-brand clothing, shoes and accessories online to a core market of 16 to 30-year-olds, also said it had made a strong start to the 2018-19 year.
Boohoo made a pre-tax profit of £43.3m in the year to February 28, up from £30.9m a year earlier and topping the £39.4m expected by analysts.
Revenue soared 97 per cent to £579.8m, ahead of company guidance. Boohoo forecast revenue growth of 35-40 per cent in 2018-19.
Mahmud Kamani and Carol Kane, joint CEOs, said: “The group made great progress during the year, integrating a new company, PrettyLittleThing, and a new brand, Nasty Gal, into the boohoo group.
“Revenue from boohoo continued to grow strongly, whilst there has been an exceptional performance from PrettyLittleThing, and Nasty Gal exceeded our estimates in its first year.
“Against a backdrop of difficult trading in the UK clothing sector, the group continued to perform well, gaining market share in the expanding online sector.
“Our international business showed higher growth rates and we are pleased with its gathering momentum.”