The programme helps anyone experiencing worry, stress or anxiety caused by health, family, work, legal or other issues.
It currently offers confidential advice to employees via a free 24/7 helpline and also provides additional emotional support through telephone or face-to-face counselling sessions.
All employees and supply chain partners are now briefed on the support Costain makes available as part of their induction process.
Gavin Bye, Costain Group SHE Director, said: “Costain has long been an industry leader on employee health and well-being issues and a natural next step was to extend our Employee Assistance Programme to our supply chain.
“We hope our decision will see other organisations across the industry following suit.
“We all experience many challenges throughout our lives which can lead to worry and stress so we felt help and support should be offered to our entire workforce, not just our own staff.
“Our Employee Assistance programme provides a superb confidential service to help us all through the difficult times that we can face in our lives.”
The Employee Assistance Programme also provides support for employees and supply chain workers experiencing issues with their physical health.
Costain provides an online portal where staff can go for mini-health checks, personalised health risk assessments and access to fact sheets on a varietyu of health topics.