Dick's Sporting Goods also says it's removing all guns from display at its store closest to Newtown, where the massacre took place.
Authorities say a gunman killed 26 people, mostly children, with a military-style rifle at Sandy Hook Elementary School on Friday after killing his mother. He then killed himself.
A statement posted on Dick's website expresses sympathy for the victims' families. It says sales of modern sporting rifles will be suspended during "this time of national mourning."
Dick's declined to answer Associated Press questions about how long the suspension would last or which weapons were being pulled.
Pittsburgh-based Dick's Sporting Goods Inc. has more than 500 stores in 44 states.
Here is their statement:
We are extremely saddened by the unspeakable tragedy that occurred last week in Newtown, CT, and our hearts go out to the victims and their families, and to the entire community.
Out of respect for the victims and their families, during this time of national mourning we have removed all guns from sale and from display in our store nearest to Newtown and suspended the sale of modern sporting rifles in all of our stores chainwide.
We continue to extend our deepest sympathies to those affected by this terrible tragedy.