"We have quite a big family but we are all really close so it has been tough for us to see someone we've always known, suffering from such a difficult disease and losing their identity.
Mr Dawkins said he was "keen to let New Zealanders know that there are things they can do to reduce their risk of developing dementia".
"Things like eating well, keeping active and staying engaged in their communities can all help reduce the risk of developing dementia."
It is estimated around 53,000 New Zealanders have dementia, a number forecast to triple to around 150,000 by 2050 as the population ages.
Alzheimers New Zealand executive director Catherine Hall said despite this, dementia "still flies under the radar".
"Our awareness campaign is about bringing dementia out of the shadows and into the sunshine. We're delighted to have somebody of Eddie's stature take time out of his busy schedule to show his support and raise awareness," she said.