Assa Abloy employs 46,000 and has sales of £6.4 billion around the world. In the UK it is best known for its Yale and Union locks and keys.
The money is being invested at its UK head office and main manufacturing centre in School Street, including the development of a new Innovation Centre.
Although new jobs are not expected as a result of the investment, Assa Abloy says it demonstrates its commitment to the Black Country site. Renovation and improvement of the existing facilities will start this summer, with a three-phase project of work due to be completed next year.
Around 600 people currently work at the site, half Assa's 1,200-strong UK workforce.
Neil Vann, managing director of Assa Abloy UK, said: “I’m very pleased to announce such a positive investment in our future and a significant commitment to our premises here at Portobello.
"Over the years we have made important improvements in our manufacturing capabilities allowing us to stay at the forefront of product development but this is one of the largest commitments we have made to the infrastructure of the site, and we believe the renovation will benefit all who work here, as well as the local residents."
He added: “We have a rich heritage here in Willenhall, as well as a proud reputation as a key employer and this investment is designed to make sure that this is continued for years to come.
"The introduction of the Innovation Centre also reflects our future-thinking and the desire to make sure that as a manufacturer we are leading product innovation and ensuring we can provide opportunities in this area for the next generation of employees.”
The plan is for significant refurbishment work inside and out at the Portobello site, which Assa says is "designed to reflect the modern methods of manufacturing used within the factory". Staff facilities will also be improved, including a new employee restaurant.
Assa Abloy is also seeking planning permission for a new car park at the rear of the site.
"Providing 100 additional onsite spaces, the new car park will not only relieve parking pressure on nearby residential areas but will also allow for a yard extension," said the company.
"The new yard will permit the more efficient and safer manoeuvring of lorries onsite and will also see the introduction of a new recycling area."
The site is already certified as 'zero to landfill' by the Carbon Trust.
The final stage of the investment will be the launch of the new Innovation Centre, intended to become the focal point of the Portobello site. It will showcase the company’s extensive investment and development of digital products, pioneered by its Yale Smart Living brand, and also act as a hub for research and development.