2018 Interim Dividend - Scrip Alternative

COSTAIN GROUP PLC

("Costain")

2018 Interim Dividend - Scrip Alternative

Costain announces that, following approval by shareholders at the Company's 2016 Annual General Meeting of the renewal of the scrip dividend scheme, elections have been made by shareholders to receive 65,892 ordinary shares of 50p each in the Company ("Shares") in lieu of cash in respect of all or part of their interim dividend for the year ending 31 December 2018, which is to be paid on Friday 19 October 2018.

Application has therefore been made for the admission of 65,892 new Shares to the Official List of the UK Listing Authority and to trading on the London Stock Exchange's market for listed securities. The new Shares will rank pari passu with the Company's existing issued Shares and dealings are expected to commence on Friday 19 October 2018.

The mandate form and the scrip dividend booklet containing the terms of the Company's scrip dividend scheme are set out on the Company's website at:

http://www.costain.com/investors/shareholder-centre/dividend-scrip/

Copies of the above forms have also been submitted to the National Storage Mechanism and are available for inspection at www.morningstar.co.uk/uk/NSM.