Cotswold Geotechnical Holdings has become the first company to be convicted under new corporate manslaughter legislation.
Alexander Wright, 27, from Cheltenham, was crushed to death when the sides of an excavated pit collapsed while he was collecting soil samples.
Cotswold Geotechnical Holdings had denied killing Mr Wright in the accident which happened in September 2008.
However, a jury at Winchester Crown Court found the company guilty of failing to ensure his safety.
The company will be sentenced tomorrow (Thursday, February 17) and could be fined a percentage of their turnover.
The Corporate Manslaughter and Corporate Homicide Act 2007 came into force in April 2008.