Vector says it will sponsor the activities of the Shareholders Association for two years.
Neither party is saying how much the sponsorship deal is worth.
In a statement, Vector's chairman Michael Stiassny says the company recognises the independence of the association and its role in helping people invest in the sharemarket.
Shareholder Association chairman Bruce Sheppard says the sponsorship was needed to ensure the future of the organisations.
He says the association faces difficulties in funding its activites.
Vector is the biggest electricity and lines company in New Zealand.