Work is due to begin in the summer on a new facility which has been hailed as a parting gift from the tyre giant synonymous with Wolverhampton.
The Goodyear workers' fund, built up over more than 30 years from sick and distress pay, initially pledged £1 million towards the project but now has confirmed it will be able to give another £500,000.
Cyril Barrett, chairman of the group of Unite members, said the community administration hub would act as a 'living legacy' of the Goodyear workers after the city's plant closed for good in August.
The redevelopment – which has been approved by Wolverhampton council planners – will see the main building on Compton Road West redesigned.
The main purpose of the hub will be to bring the charity's range of support services including inpatient care, care in the home, daycare facilities and psychosocial care, under one roof, creating a single point of access for healthcare professionals and families.
A link between the hall and the hospice accommodation will be created.
Mr Barrett, from the Goodyear workers 5/344 Transport and General Workers Sick and Distress Fund, said members were proud something positive would come from the closure of the landmark plant, which resulted in hundreds losing their jobs.
He said: "We held 20 meetings with members and the one thing they made clear was supporting Compton Hospice was a priority.
"Planning permission has been granted and hopefully in the middle of next year we will see the start of the process of building the communication centre."
He added: "It is so important to us. The hospice has provided care and support to families of many of our members. This is a project we wanted to do.
"On behalf of my colleagues, I am absolutely delighted and so proud.
"What we are doing is what we promised, creating a living legacy to good, honest, hard-working people who have been members of the fund since 1985."
Mr Barrett said the workers' group, which has supported countless charities across the Black Country, had budgeted to be able to give £1.5 million but was only now in a position to confirm it could provide the full amount.
It means hospice bosses will not have to apply elsewhere for additional funding.
Compton Hospice chief executive Claire Marshall said: "It's so exciting.
"Patients' needs are getting more complex and we want to serve more patients than we ever have. It means we will have a really good, co-ordinated service.
"We co-ordinate care between GPs, hospitals and other care providers. Having this facility is essential going forward to help provide a seamless experience for patients."
Ms Marshall said hospice bosses had been overwhelmed by the support of the former Goodyear workers.
She said: "£1.5 million is a vast amount of money by anybody's measure and the fact is is coming from the community which has supported us for decades is amazing.
"It came as a surprise, certainly the scale of it. When it started, to get £1 million we were just euphoric. Now it has been extended to £1.5 million - the whole cost of the project - is just incredible."
After securing planning permission for the extension, finding the extra money needed for the scheme means Compton has now passed the final hurdle.
Work is expected to take between six and nine months to complete.
Fund secretary and former Goodyear worker Paul Bough said: "Everyone has got some sort of affinity with Compton Hospice, their family has been helped.
"The sooner it is completed the better."