Total sales at Reiss rose by 19.7% year on year in the six weeks to 7 January thanks to growth in its UK like-for-like sales, ecommerce sales and international expansion.
Reiss said its gross margin remained “robust”, although it did not provide further detail.
UK sales grew by 11.6% during the period, boosted by a strong performance both online and in stores.
International sales rose 69.4% following the opening of new stores and concessions, and entry into a number of new markets.
US private equity firm Warburg Pincus acquired a majority stake in the business last April. Between April and December, Reiss opened almost 30 new stores.
As of December, the firm had 189 stores in 17 countries, up from 160 stores in 15 countries six months earlier.
The business said: “As we enter 2017, we look forward to working with our new partners at Warburg Pincus to expand the business further into a truly global fashion brand.”