The charity helps people who feel lonely or socially isolated because of age, disability or poor mental or physical health.
Jo Ivens, CEO of Impetus, said:
"The Mayor's been a great friend to Impetus and the walk he's organised is an inspiring event which its fantastic to be involved in.
"When you realise that around £10 pays for a whole week's befriending, it gives you some idea of the difference the 5k we're hoping to raise could make to people's lives."
The event has been organised to raise money for the mayor's chosen charities and to help pioneer a new designated pathway, the Brighton & Hove Way. Impetus is aiming to raise £5000 through their participation in the event.
Pete West, the Mayor of Brighton & Hove, added:
"I love the work Impetus does to provide vital support for lonely and socially isolated people.
"It's a local charity that's really close to my heart as it very much reflects Brighton's inclusive and community-minded spirit. I'm delighted that they've got such a big involvement in the walk."
If you'd like to join the Impetus team - on 30th April 2017 - for the sponsored 18 mile walk around the city or for more information about how you can support Brighton & Hove Impetus, email Fundraising Manager Alex Mackain-Bremner at firstname.lastname@example.org