The three new sponsors have a combined customer base of 18 million and 2,740 outlets, which will more than double the current number of outlets where collectors can earn points.
Vodafone's 13.2 million customers will earn Nectar points on phone usage and on some purchases in Vodafone stores.
Loyalty Management UK (LMUK), which runs the scheme, said the new entrants had the potential to bring up to three million new Nectar collectors to the programme.
Chairman of LMUK Keith Mills said: "This is a tremendous growth opportunity for Nectar and really sets us apart from other reward programmes. Adding three new leading UK brands to our portfolio means we will have even more to offer key audience segments, especially men and the younger end of the market."
A spokeswoman for Sainsbury said: "For over 11 million customers this means even more retail outlets for them to collect points."
The Nectar programme, launched in September 2002, has a reported 11 million active cardholders who have used the card in the last three months.