The reasons given by those interviewed for the report included cultural stigmas, lack of faith that authorities would act on complaints, and the fear that they would be thought too vulnerable to be sent on future assignments.
But the CPJ has interviewed more than 50 journalists over the last few months about previously unreported sexual assaults.
The CPJ report, written by senior editor Lauren Wolfe, comes after CBS News correspondent Lara Logan (pictured) was sexually assaulted in Cairo while reporting on demonstrations in Tahrir Square.
According to the report, the widely-reported attack on Logan "brought the issue into sharp focus" and "accelerated changes in attitudes across the profession", prompting many journalists to come forward and talk about experiences of sexual assault.
Over the past four months, CPJ has interviewed 27 local journalists working in the Middle East, South Asia, Africa and the Americas, and 25 international journalists. The majority of those interviewed were women, the report states, but some men also came forward.
Five of the local journalists described being brutally raped, according to the report, while others reported various levels of sexual assault, aggressive physical harassment, and threats of sexual violence.
Two of the international journalists reported a rape, while five others described serious sexual violation and 22 said they had been groped multiple times.
In the wake of the attack on Logan, several news organisations are adapting their security training to take into account civilian threats such as assault, as well as battlefield hazards.
Thomson Reuters is reportedly altering its security training and protocols for journalists, including adding training to help journalists navigate crowds like the one in which Logan was attacked. Larry Rubenstein, general manager for safety and logistics for editorial, said the attack on Logan prompted the changes to its policy.
"The Lara Logan case drove the point home, that we must prepare our journalists not only for the battlefield but for all of the various new threats they face when covering the news. But we've been seeing it for some time and are continually reviewing our training."
The CPJ has also issued new guidelines alongside its report.
Rodney Pinder, director of the International News Safety Institute, which contributed to the report, said that the report marked the most significant step forward for safety for female journalists since the INSI's own report six years ago.
"For that survey, which was the first of its kind, we looked specifically at safety issues in the field for female journalists.
But at that time there was some resistance from female correspondents into us looking at safety issues related to women, for fear that assignment editors may take the easy view that if women are going to have all these problems it is easier not to send them.
"So there was reluctance too for women to take part in our survey.
"I think that this [CPJ] report, coming on the heels of the appalling Lara Logan attack, will bring the issue into better focus and bring more attention.
"What we've got to do now is take this forward and see what can be done about it in terms of practical training for women working in the field."
The INSI has recently been training female journalists in the Congo, and is planning to run a similar programme in Afghanistan in the near future, Pinder said.