Hamburg Police said 18 people were injured in the attack at the northern city's Central Station at about 18:00 local time (16:00 GMT) on Friday, News.Az reports, citing BBC.
Officers arrested a 39-year-old German woman at the scene as they carried out a major operation.
The woman remains in police custody and is scheduled to appear in court on Saturday.
In a post on X, Hamburg Police said several people who were hurt had sustained life-threatening injuries.
Speaking to the press outside the station, police said they believe the suspect acted alone and did not have a "political motive".
Rather, they believe she may have been "in a state of mental distress," Florian Abbenseth, a police spokesperson, told reporters.
Police later added that its homicide division is investigating the incident as well as the suspect's motives.
The attack happened between platforms 13 and 14 - which are accessible via a busy main road - while a train was on one of the platforms.
Some of the victims were treated inside trains, according to reports.
German Chancellor Friedrich Merz said the attack was "shocking" and thanked the emergency services on the ground for "their rapid assistance".
