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.