US Defence Secretary Chuck Hagel said the results showed victims were more confident the military would take their cases seriously but voiced concern that large numbers of male victims were still unwilling to report being sexually assaulted.
The Pentagon's annual report on sexual assaults "underscores that we have a long way to go before we get close to solving this problem," Hagel told reporters.
The Pentagon recorded 5,061 reports of sexual assault across the military last year, compared to 3,374 in 2012.
Citing estimates that more than half of all victims of sexual assault in the armed forces are men, Hagel said he had ordered measures designed to encourage more male troops to come forward.
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Heavy drinking is often cited as a major factor in sexual assault cases and Hagel said he had ordered a review of alcohol policies to address "the risks that alcohol is used as a weapon against victims in a predatory way."
More perpetrators also were being disciplined and charged in court-martial proceedings, Hagel said, citing the report.
In cases where the department had legal jurisdiction, commanders had sufficient evidence to take disciplinary measures against 73 percent of offenders, compared to 66 per cent of subjects in 2012, according to the report.
The spike in reported assaults comes after a flurry of initiatives designed to reassure victims and bolster investigations.
US Senator Claire McCaskill, one of several female lawmakers that has focused attention on the issue and pushed for reforms, said the report showed "concrete progress.