The Release Me hitmaker also asked people to keep his wife Patricia, who suffers from Alzheimer's, in their thoughts.
New Zealand fans will know Humperdinck for his song Ten Guitars - a B-side for the Release Me record.
Humperdinck - who has four children, Scott, Jason, Louise and Bradley, with his spouse - added: "My biggest 'ask' is for my darling wife, Patricia (Popea) She has been through so much and does whatever it takes. She is an unbelievable woman of strength. Please also keep our wonderful caregivers in your prayers. Thank you, Engelbert"
The Last Waltz singer's wife - who he married in 1964 - has had Alzheimer's for more than a decade and receives around the clock care at their Bel Air home.
In 2019, Humperdinck shared his joy at Patricia calling him by his name and speaking to him for the first time in years.
He said at the time: "She hasn't spoken for three years, she even called my name three days ago which is wonderful to hear. It's the best Christmas miracle ever. I'm thrilled."