Alibaba Group's plan for a potentially record-breaking initial public offering is prompting other companies to push back their own stock-market debuts.

The Chinese e-commerce company is aiming to go public in a sale that could raise more than $20 billion soon after Labor Day, historically a prime time for IPOs. Other companies are now worried that investors and bankers will be too focused on the giant Alibaba deal to give them enough attention, according to people familiar with the deals.