John Lewis-owned department store Peter Jones will switch to seven-day trading this autumn, following the completion of a five-year,£100 million overhaul.
About half of John Lewis's 26 department stores have adopted the practice, but by next year it hopes 23 stores will have voted to make the switch.
The Sloane Square end of Peter Jones will reopen on June 1, but the furniture floor will not be reinstated until the end of the month.
The refurbishment has increased the trading area from 138,000 sq ft (12,820 sq m) to 172,000 sq ft (15,980 sq m), and the space devoted to women's fashion will double.
Peter Jones managing director Beverley Aspinall said fashion brands would be given a stronger identity on the enlarged floor.