Crane hire company Eurolift Tower Cranes and its parent WD Bennett Plant & Services have been found guilty of two health and safety breaches over the 2005 Worthing crane collapse.
Gary Miles, 37, from Crowthorne in Berkshire, and Steven Boatman, 45, from Reading, died after an untrained colleague loosened the wrong bolts on a 36m-high tower crane when trying to dismantle it.
Colleague, Dave Smith, sustained broken bones in the collapse.
All three men were employed by Aldershot-based Eurolift (Tower Cranes), a subsidiary of Gloucester firm WD Bennett Plant & Services.
Eurolift admitted two safety breaches – one under the Health and Safety at Work Act and another under the Construction (Health, Safety and Welfare) Regulations. But WD Bennett had denied its two charges.
The jury for the trial, which began on 16 March, took just two-and-a-half hours to return a majority verdict.
Both companies will be sentenced on another date, yet to be set.