A police spokesman said: "The couple agreed to pay for extra officers. They will ensure minimal disruption."
Lily and Sam's wedding is set to take place in the village of Cranham, near Stroud, and the main road around the area will be closed, although residents will be given passes for access.
The 26-year-old singer will celebrate her nuptials by spending her honeymoon with Sam, 32, in luxury £1,000 tepees in the backstage VIP area at the Glastonbury Festival – and event organiser Michael Eavis has vowed to make their celebration "special".
He said: "Lily's coming down for her honeymoon. We'll look after her, I'll set her up a special tent - she'll get well treated.
"I'm going to the wedding in Gloucestershire. I've known her since she was tiny. She's such a star isn't she? I'm really looking forward to her wonderful wedding."