Robin MacGeachy, of Peak Scientific Instruments, was speaking as Shadow Business Secretary Chucka Umunna made a visit to his business.
Mr MacGeachy said a deal for a new plant at Inchinnan Business Park in Renfrew will not go ahead if there is a Yes vote because of "uncertainty" over the economic implications for his business.
While Mr MacGeachy stressed that jobs at the existing site would be safe if Scots vote Yes, he said the firm will opt to expand overseas.
He said the company, which manufactures gas generators, was already struggling to recruit enough engineers and he fears the situation will worsen under independence because more graduates could leave Scotland to work abroad.
The firm, which sells goods to 110 countries, employs more than 300 people internationally and has won the Queen's Award for International Trading.
Mr McGeachy said: "We have plans for a new site next door but those plans are on hold.
"Business requires some longer-term certainty. There are unanswered questions and these will take time to address.
"Being Scottish is very important as I travel around the world. However, so is being British. If we are on own I believe it dilutes the message we have about being a great country within a great union.
"London is seen worldwide as a centre of global finance and a place to do business and is part of our country today. If independent it is in another country. We have won our fourth Queen's Award this week, again a very strong message around the world where the Queen and UK is looked up to."
Mr Umunna said: "In many respects this company is a symbol for what the union brings for a Scottish and UK business. It is the kind of company we want to see thrive.
"The owners are absolutely clear that Scotland remaining part of the union is crucial for their business because it gives you a seat at the top table globally and our membership of the EU gives you access to all the new emerging markets."
However, international manufacturing investor Ivan McKee, said: "It is also important that businesses ask serious questions of the No campaign - what has Westminster to offer to boost growth in the Scottish economy, and tackle the key challenges we face?
"I believe businesses will find the Westminster government has very little that is positive to offer them in terms of policies that are designed for the Scottish economy. Many international companies - including Scottish companies with a global presence - have invested and continue to create new jobs in Scotland."