Phil Loney, chief executive of mutually owned Royal London, said that it would reconsider whether its 1200 employees in Scotland could continue to service customers across the UK if there is a "yes" vote in September.
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The organisation, whose roots in Scotland date back 133 years, already plans to drop the Scottish Life brand.
Mr Loney said: "We have a significant part of our business in Scotland. We have a third of our people in Scotland."
But he said that most of its customers were elsewhere in the UK.
He added: "It would take a lot to uproot us from Scotland. We are quite committed to it. But if the people of Scotland did want independence, it becomes a foreign country and we do what we do with any foreign markets: we look at it and decide whether it looks attractive."
The former Scottish Widows executive said that currently, Royal London employees in Edinburgh and Glasgow handle clients across the UK. But he added that in the event of separation, it would view Scotland as it does Ireland, where it operates Caledonian Life.
Staff there only look after Irish customers because its use of the euro and other issues make it less attractive for them to service the UK market, Mr Loney said.
"We do not do that for Scotland at the moment," he added. "We would start to do things like that if Scotland chooses to become a foreign country." He continued: "We have no desire to leave."
Scottish Life was formed in Edinburgh in 1881. In 2001, it transferred its business to Royal London in a £1 billion deal that handed windfall payments worth thousands of pounds to Scottish Life members.
Scottish Life remained as a brand for Royal London's pensions business. Royal London said in October it plans to phase out the Scottish Life brand and the 176-year-old Scottish Provident name it acquired six years ago, to unify its offering under the Royal London badge.
Ivan Mckee, a director of pro-independence group Business for Scotland, said: "Many Business for Scotland members manage global businesses successfully at present, they look forward to the economic benefits and opportunities independence will bring to their businesses in Scotland and see no reason to incur significant staff relocation costs for no tangible benefit."
A Scottish Government spokesman said: "Scotland is home to a diverse range of financial services companies, including large multi-nationals, and as part of the European single market an independent Scotland would continue to provide services to customers across the UK."
Scottish Life had a strong 2013, with pensions sales up 26% to just under £3 billion for the 12 months to December 31. Protection sales were down 15% to £436 million as the wider market continued to struggle.
Scottish Life has been a beneficiary of the introduction of auto-enrolment into pension schemes in many workplaces. Some 67,000 new customers joined its workplace pension schemes over the year.
Group pensions sales were up some 56% on last year, following 21% growth in 2012.
Mr Loney said that its pensions sales growth was "broad-based" and included a 13% rise in personal pensions sales in a declining market. It was also strong in income drawdown.
Last month, the Government said it is delaying the introduction of a cap on pension charges for at least a year. Mr Loney said: "We are very pleased that, by all accounts, the Treasury has been asking some tough questions of the DWP (Department for Work and Pensions) about whether this is a good idea."
He warned that a cap would become a de facto floor on charges.
"One of the reasons some of the big shareholder-owned companies want a price cap, like Legal & General, is it can become the pricing norm that prevents prices falling further and they can trap some of these gains in dividends for their shareholders."
L&G declined to comment.