Existing investors in Shein Global Holdings Ltd. are agreeing to a lock-up on new shares allocated to them in the fast-fashion retailer's Hong Kong initial public offering, according to people familiar with the matter.

The investors will join cornerstone backers in pledging not to sell their IPO shares for a period of six months to signal confidence in Shein, the people said, asking not to be identified discussing private information.

The lock-up arrangement covers new shares distributed to current backers participating in the Hong Kong listing. By aligning with cornerstone investors, the existing shareholders are committing to hold their stakes through the early trading period.

Such agreements are common in major IPOs and are designed to prevent immediate selling pressure once shares begin trading, helping stabilize the stock price in early sessions.