Parker, who was mayor during the 2010-11 quakes, is in a hospital care facility in Christchurch after suffering a heart attack, which was followed by a stroke late last year.
The inspirational leader who during the dark days of the quakes was the voice of reassurance to Christchurch residents vowed last month despite his ill-health that he hoped to attend today's national memorial service.
And today, he was able to be among the hundreds who gathered at the city's quake memorial on the banks of the River Avon with a message for his city.
"It was a nightmare that was delivered on that mild sunlit late summer's day – a moment that changed everything and everyone forever - a moment that caused a level of destruction and casualty that none of us will ever forget.
"For those who were not here at the time, it would be difficult to really understand what we felt, what we shared, what we lost. Those who were here, or whose loved ones were here, share a bond that is impossible to explain beyond this place."
He added: "So many families still carry the pain of loss. Our thoughts are with you all and we will never forget the mothers, fathers, children and wider whanau that you mourn every day. Today we also put our arms around those amongst us who are still carrying injuries and memories that won't go away. So many of you have faced ongoing difficulty and disruption to your lives.
"We also say a heartfelt thank you to all of you who came from throughout New Zealand, from around the world, to help us at our time of need. We will never forget what you did for us.
"On this day we also remember the collective community spirit that lifted us in our most difficult hours. May the aroha from that very same community give you strength today."
Parker, 68, felt at his fittest when he had a heart attack in the early hours of May 3 last year.
The former This is Your Life host was treated and received medication including blood-thinning drugs for his initial medical event.
Then, seemingly well-recovered, he had a stroke on the morning of October 5 - just days after he attended an event in Akaroa to mark the restoration of the historic lighthouse.
He collapsed at his Christchurch home with the life-threatening stroke causing an intracerebral haemorrhage (ICH), which is bleeding within the brain tissue.
Parker spent 11 days in Christchurch Hospital's Intensive Care Unit in a critical condition before being transferred to a general ward for a further two to three weeks' monitoring.
Then followed 11 weeks of care and rehabilitation at Burwood Hospital, where he had two smaller strokes, before he moved to his current care facility last month.
His wife, Lady Jo Nicholls-Parker, is full of praise for the medical treatment her husband has received.
"At every stage of Sir Bob's illness, he has had the most amazing care and support from hospital staff at all levels," she said.
"We cannot speak highly enough of our health system. Staff have been exceptional. We both just want to say a huge thank you to everyone who has contributed to his care."
The stroke has affected movement on Parker's left side and he is currently in a wheelchair.
"Although Sir Bob is now in a private facility we intend to continue with the occupational therapy and physiotherapy treatment established at Burwood to improve his movement," Nicholls-Parker said.
Christchurch-born Parker served two terms as the city's mayor from 2007 to 2013.
His tenure spanned the 2010 and 2011 earthquake sequence which devastated the city, and on February 22, 2011, claimed the lives of 185 people.
With his fluoro-jacket, Parker was an ever-present face in the quake's aftermath, leading recovery efforts, working alongside the police, army, and international rescue squads, and dealing with the media's questions.
