"The values of honor and trust are the lifeblood of our military, and every act of sexual assault directly undermines those values. So too does every act of retaliation against those who report these crimes," Carter was quoted as saying on the US Department of Defense's (DoD) website on Friday.
In April, the DoD observes Sexual Assault Awareness and Prevention Month, which is aimed at raising awareness and helping to prevent such cases.
"This is an important opportunity to remind ourselves why ridding our ranks of sexual assault and sexual harassment is so critical," the defense secretary said.
He called for efforts to ensure an environment where sexual assault was neither condoned nor ignored. Carter said it was important to reinforce a culture of prevention, accountability, dignity and respect.
On March 19, the US Government Accountability Office (GAO) said the US military must undergo a culture change to combat sexual assaults among male and female service members.
According to the GAO data, more than 1,000 male and 4,000 female service members reported sexual assault in 2014.