Freshwater, a privately held company based in Colorado, has developed a suite of products focused on network and systems management and performance monitoring.
The purchase will give Mercury the product suite as well as Freshwater's 3,000 customers.
"We see a great synergy between our companies and a natural fit to our software solutions," said Mercury president and CEO Amnon Landan.
Mercury now intends to develop an integrated product combining flavours of its own offering with those of Freshwater. Mercury claims IT organisations will now be able to see a combined view of application performance data that will enable them to collaborate and deliver greatly enhanced e-business performance.
On completion of the deal, Freshwater will operate as a wholly owned subsidiary of Mercury, under its Application Performance Management division. Four of the five Freshwater co-founders will remain, while president and CEO Donna Auguste will leave to "pursue philanthropic interests."