Willis will join Costain on Monday for a week’s handover period with current CFO Tony Bickerstaff who is leaving the business on November 30 after 14 years in the job.
Her previous role was chief financial officer at banknote printer De La Rue.
Willis stepped down from the role in January after less than two years following a series of profit warnings.
Prior to De La Rue Willis worked at Premier Farnell between 2014 and 2017, including as chief financial officer from 2015.
She has also held senior finance roles at Pelican Rouge, AZ Electronic Materials, and HSS Hire.
Dr Paul Golby CBE, Costain chair, said: “We are delighted to welcome Helen to the Board and look forward to working with her. She has a wealth of financial experience and I am confident she will add significant value to our team.”
Willis said: “I am hugely excited to be joining Costain and supporting Alex and his team to maximise the opportunities within the UK infrastructure market.”