The Swindon-based company has acquired MSI from Empire Investment Holdings for a cash consideration of $6.5 m (£4.1m).
MSI operates a hospital sterilisation facility in New York and is said to be the second largest provider of these outsourced services in the US. It recorded revenue of $4m (£2.5m) for the year to 31 December 2011.
Synergy Health said the acquisition of MSI is an early step in its plans to develop a hospital outsourcing base in the US. The company will work with MSI's customer base to expand its knowledge with the view of developing a networking in 2013.
Synergy Health chief executive Richard Steeves said: "The acquisition of MSI is an exciting first step for Synergy into the US hospital sterilisation market.
"By having a small, but low risk entry point into this market, we will be in a position to fully research the requirements of the US healthcare market and set ourselves up for a progressive expansion of the service in 2013."
The company made its first US acquisition in April 2011 when it purchased BeamOne, a provider of e-beam medical sterilisation services. Synergy Health announced the acquisition of Switzerland-based Leoni Studer Hard for £39.7m (€47.6m) earlier this week.