The firm has been providing support to patients and families affected by cancer since 1911.
Memoria, which owns and runs the Barnby Moor Memorial Park and Crematorium in Ranby, has donated hundreds of thousands of pounds donated over the past 18 months to Macmillan.
Howard Hodgson, chief executive of Memoria, said: “It’s estimated almost 400,000 people are diagnosed with cancer in the UK each year and it can have a devastating effect not only on the patients, but their families too.
“At Memoria, we work closely with Macmillan and we see first-hand the incredible support they provide at their times of need.
“Charities such as Macmillan do vital work in communities across the UK on a daily basis, but they need support now more than ever.
“We’re proud of our close relationship with Macmillan and we will continue working together to bring comfort to bereaved families when they need us most.”