REUTERS/Mike Blake
According to a survey of 100 CEOs from accountancy firm KPMG, 76% are considering relocation, while 72% said they voted to Remain in the European Union in the June referendum.
Despite the vote to leave the EU, CEOs are still confident in the economy and their own abilities - 69% said the UK's economy would grow in the next year and 73% said their own companies would also grow.
The CEOs were picked from companies with revenues ranged between £100 million ($129 million) and £1 billion.
"CEOs are reacting to the prevailing uncertainty with contingency planning. Over half believe the UK's ability to do business will be disrupted once we Brexit and therefore, for many CEOs, it is important that they plan different scenarios to hedge against future disruption," Simon Collins, KPMG's UK chairman, said in an emailed statement.
"In our own work, we have seen international clients who had been considering basing European headquarters in the UK, opt for Ireland instead."
Financial services jobs have been the first to show signs of Brexit stress. The number of new financial jobs in England dropped 10.1% following the Brexit vote in June, as uncertainty over the UK's future membership of the single market hurt job market confidence.
Finance vacancies fell in every region in July and August, according to the Institute for Public Policy Research, an influential think tank. London saw a 13.6% drop in job adverts, including for administrators, managers, and chief executives.
Meanwhile, the number of people applying for finance jobs in Dublin rose by 800%, according to staffing and recruitment firm Manpower.