Some workers had stones and sand thrown at them and others have had threats that they would be poisoned.
DOC deputy director-general of people and engagement Karen Jones said the increasing number of threats was having a cumulative impact on workers.
She said the threats were becoming more personal and delivered both through social media, and in person.
Jones said staff were urged to report any threat. Those reports were then passed on to police.
She said there had been threats to shoot staff, which were immediately referred to New Zealand Police.
Jones said the use of 1080 was the cause for a lot of the threats but there was also anger from some about how DOC undertakes concession compliance, whitebait control and campground fees.
She said having to respond to the threats diverted attention away from the work DOC was charged with carrying out.
Forest and Bird have criticised the anti-1080 groups for targeting DOC workers.
The group's chief conservation advisor, Kevin Hackwell, said Forest and Bird members had also felt the force of the anti-1080 groups' anger.
He said an 80-year-old member was knocked to the ground by a protester and another had his tyres slashed.
Hackwell said anti-1080 groups needed to stop channelling their anger towards conservation workers.