As the last person hired, he was among the first to be made redundant.
The Employment Relations Authority (ERA) said Warner had applied for the wage subsidy for its staff and Hedgman was paid until mid-June.
Warner Construction said it had no choice but to make staff redundant - organisations it would normally work with, particularly local authorities, put a hold on new civil projects.
Warner said about 60 per cent of its contracts were cancelled almost immediately.
There were 16 staff, including Hedgman, among the first group of redundancies.
The ERA said Warner failed to follow the proper process and consult with Hedgman before the decision was made.
"Mr Hedgman accepted Warner's situation was such that his redundancy was both inevitable and substantively justified," the ERA said in its decision.
"It was the process and lack of communication with which he took issue and which led him to conclude his dismissal was unfair."
The ERA concluded Hedgman's dismissal was unjustified.
It said he was entitled to close to $4000 in lost wages and $10,000 in compensation for humiliation, loss of dignity and injury to feelings.
- RNZ
