More than a dozen women who worked at five United Nations agencies over 10 years, whose names are being withheld because they fear workplace retaliation, described a system that they said was stacked against them. Some said they were accused of being overly emotional when they tried to report an incident. Others described being verbally abused for seeking to report it.

Mr. Dujarric, the spokesman for Mr. Guterres, said the secretary general led discussions on the issue at a May meeting of the United Nations Chief Executives Board. He said the board had agreed to changes in reporting, investigation and decision-making procedures, like recruiting better-trained investigators and building a database of employees fired for sexual harassment, to avoid rehiring them at a different agency.

The process for investigating misconduct is so unpredictable, some critics say, that victims of harassment or abuse don’t know whether they will be discouraged, taken seriously or penalized for coming forward.

One woman working for the United Nations in Iraq described how a male colleague, who sometimes shared videos demeaning women, told her how happy he was to have “loose and sexy women” from Ukraine and Lebanon in the office. When she tried to file a complaint, she said, she was discouraged by an ethics officer who told her the insults did not count as harassment.

A woman at an agency headquarters in New York described seeking advice for a friend about reporting an assault, only to find out that she was required to report what she knew, even without the friend’s consent. Moreover, she learned, she and her friend’s names could be shared with the accused, making her nervous about retaliation.

“I don’t think this guy is going to come with a gun to my house or something, but on the other hand, you never know,” she said.

Investigators at some United Nations agencies described their work as operating in a gray area. They conduct internal reviews that can lead to punishments like termination; they are not criminal investigators prosecuting offenders.