Penny Bright's memorial service will take place at St Matthew-in the-City in Auckland on Sunday afternoon.
Ms Bright died earlier this month of ovarian cancer. She was 64.
More than 100 service programmes have been printed in anticipation of the celebration of her life.
Fellow activist and friend Lisa Prager says anyone who supported and respected her is welcome.
"Penny was a brave and courageous woman. She stood up for what she believed was right, a person who believed in truth and justice. We're going to celebrate all of those values."
Ms Prager encourages people to bring a long a banner, sign or potted plant to the service, at 2pm.
"We'll hear from the people who knew and loved her, the people who stood shoulder-to-shoulder with her at protests and at council meetings."
She says it's the closest thing we'll get to a state funeral for a fallen "warrior".
"Penny was one in a million. She was a woman warrior, and deserves our respect, our love and a fine farewell."
- Penny Bright was a 'kindred spirit' - John Banks
- Penny Bright 'a fighter and a warrior for truth and justice' - Lisa Prager
Last week friend and political rival John Banks praised Ms Bright.
"She was a rebel without a pause. She had determination through her veins. Her heart was always in the right place. Yes, she could be dogmatic, pedantic, obsessive, obstructive and all of those things, but in hindsight she gave us periodic cold showers - and kept us on our toes."
He visited Ms Bright on her deathbed a few weeks ago.