The 29-year-old, one of seven Scotland-based full-time professionals, has featured in 42 one-day internationals and 24 Twenty20 internationals.
He said: "It has been an incredibly difficult decision but one that I felt I had to make at this stage."
Scotland head coach Grant Bradburn described it as "a big loss".
South Africa-born Mommsen led Scotland at the 2015 World Cup in Australia and New Zealand and the 2016 World Twenty20 in India.
He scored two hundreds and six half-centuries in ODIs, where he averaged 32.38 with the bat, and was named ICC Associate and Affiliate Cricketer of the Year in 2014.
His best form came in the 2014 World Cup qualifier in New Zealand, where he hit 520 runs at an average of 86.66 during the tournament, including 139 in Scotland's victory over the United Arab Emirates in the final.
Mommsen was also the first to captain Scotland to victory in a global tournament when they beat Hong Kong at the World T20.
"Above all, we are very happy for Preston to be offered such an exciting opportunity," added Bradburn.
"Preston is intelligent, well respected and ambitious, so for him to be moving into a corporate field that he is passionate about is just brilliant, but he offers the team many qualities that will be difficult to replace.
"A quality experienced batsmen at the peak of his skills, consistently our fittest player, top fielder and, of course, our leader with a tough uncompromising attitude."
Cricket Scotland chief executive Malcom Cannon also praised Mommsen's contribution.
"Preston has been an exemplary ambassador for the sport in this country and should be extremely proud of his achievements as captain of Scotland," he said.
"He has raised the bar in the level of professionalism he has shown."
Mommsen predicted that Scotland "will continue to grow its presence on the global stage in the future".
Scotland captain Preston Mommsen has retired from international cricket to take up an "attractive opportunity in the corporate world".