The two Home Retail Group businesses raised the landmark amount in just 21 months, smashing through their initial fundraising target of £2.5m for the group's official partner charity Teenage Cancer Trust.
The money will go towards the construction and maintenance of 22 teenage cancer units within NHS hospitals across 20 towns and cities in the UK and Ireland.
The charity partnership was set up in July 2010, and since then the fundraising activities by the two retailers have contributed towards creating and maintaining 162 beds, equivalent to 4,176 inpatient stays and 5,568 outpatient visits by young cancer sufferers.
Staff from Argos and Homebase have taken part in a wide variety of fundraising events such as store-to-store travel challenges, a human greyhound race, a naked calendar, a Mad Hatters Tea Party featuring strange hats. One keen shop worker from Essex even got 'I Love Argos' tattooed onto his leg to raise money for the charity.
Home Retail Groups chief executive Terry Duddy said: "Teenage Cancer Trust has really struck a chord with our people across the Group who have gone to remarkable lengths to help raise money and make a difference to the lives of young people affected by cancer in the UK and Ireland.
"Thanks to these efforts and the generosity and kindness of our customers we have managed to raise an amazing £3 million for Teenage Cancer Trust. The fact that we have reached and exceeded our original target of £2.5 million earlier than planned is testament to the hard work and dedication of all involved."
The charity's chief executive Simon Davies added: "We have been blown away by the dedication and enthusiasm of Argos and Homebase colleagues and customers. These vital funds are making an enormous contribution towards our goal of reaching every young person with cancer and we can't wait to see if we can reach the magic £4 million milestone by the end of our partnership in February 2013."
Further charitable initiatives that Home Retail Group will be supporting include the launch this May of the Entertainment Exchange. Working in partnership with musicmagpie.co.uk, from 1 - 31 May, colleagues and customers are invited to drop off their unwanted or out-dated music and film collections in the designated Entertainment Exchange drop off bins in Homebase stores. Teenage Cancer Trust then receive a donation in return.