McEvoy will join Verity to become executive vice president of products and services at the company, which makes text search software. He will be replaced at Sybase by former Powersoft division president David Litwack.
The resignation follows Sybase's ouster last month of its president and CEO Mark Hoffman, who was replaced by another former Powersoft executive, Mitchell Kertzman.
Sybase has reported losses in its last two fiscal quarters, and in July announced that it plans to layoff between 600 and 700 employees. The company has long been the number-two player in the database market but has been consistently losing ground both to market-leader Oracle and Informix Software.
Among other duties, McEvoy was tasked with driving the development of Sybase's SQL Server 11 database server, an update which shipped earlier this year and was intended to resurrect the company's reputation as a technology leader following the shipment of a bug-riddled previous version.
McEvoy joined Sybase in 1994 from Bachman Information Systems, which has since merged with Cadre Technologies to form Cayenne Software.