Serco Group PLC (LON:SRP) said chief operating officer Ed Casey will step down at the end of year to take a role with a US company.
Casey, who has been with the services group for the past 12 years, has spent four years doing a weekly commute across the Atlantic and wants to return home to the US.
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Serco did not disclose details of Casey's new employer but said it was not a competitor.
"Whilst we are very sad that Ed is leaving, we completely understand that after four years of weekly commuting across the Atlantic, he would like to have a job closer to home,” said chief executive Rupert Soames.
"I would like to place on record our sincere gratitude for all he has done for Serco over the last 12 years, and in particular helping to lead the company through the critical early years of the transformation of our business."
Serco, which provides justice, transport, defence and welfare services to governments, has been trying to turn its business around following a series of profit warnings.
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The company started a five-year restructuring programme after its profits took a hit following an electronic tagging scandal in 2013. Serco was referred to the Serious Fraud Officer for charging the Ministry of Justice for tagging prisoners who had been released or died.