The supermarket chain's Rice Pops from its Basics range are now being sold in plastic bags and there are plans to drop cardboard boxes from all its own-brand cereals.
Sainsbury's is also joining Waitrose in selling milk packaged in plastic bags, which can then be emptied in to a reusable jug by consumers at home.
This uses 75% less packaging than traditional plastic milk bottles.
Sainsbury's had conducted a poll among customers to see what they thought the most over-packaged products were and cereal was deemed one of the worst offenders.
Stuart Lendrum, head of packaging at Sainsbury's, told The Times: "When it comes to cereal, our customers asked us why they need to be in a box as well as a bag when you can just print all the information on the bag."
Some customers are worried that a plastic bag alone will not be robust enough to stop cereal from getting crushed.
The Daily Mail reports that Kellogg is considering replacing cardboard boxes with other packaging as long as they can provide the same quality of product.