The financial services firm said it hoped to raise more than £2m over the three years to be shared by the charities, which were chosen by a staff vote.
In addition to fundraising, the firm will support the charities with its expertise in areas such as strategy advice, analytics, finance and project management.
Deloitte will work with the Alzheimer’s Society on a project called Care for Today, Cure for Tomorrow, which will help fund research into the treatment and prevention of dementia. Employees will offer business skills to improve the charity’s efficiency.
Through its work with Mind, the company aims to reach more than 10 million people in three years to raise awareness of mental health issues. Its staff will help to create training programmes and introduce technologies to help raise awareness. They will also provide accounting, tax and audit advice.
Deloitte will work with Prostate Cancer UK on its Search and Rescue programme and aims to reach more than 300,000 people through workshops around the UK.
Bob Thust, director of responsible business at Deloitte, said: "We want to offer more than the typical fundraising, which often offers only a temporary solution, and aim to make a real difference for each of these charities.
"By using the skills and expertise of our staff, we believe we can leave a lasting legacy that will continue to help each charity long after the partnership comes to a close."