"The strikes by (train drivers' union) GDL cost us a lot of money," Deutsche Bahn chief executive Rüdiger Grube told a news conference.
The figure of "more than €150 million" included the cost of train cancellations, contingency timetables, ticket reimbursements and the cleaning of the trains during the industrial action, he said.
The GDL union called six walk-outs between September and November, hitting both cargo and passenger trains, over demands for wage increases and shorter working hours.
GDL also wants to represent other categories of employees within Deutsche Bahn, not just train drivers.
A deal still has not been reached and several more rounds of talks are scheduled for February.
The first round of negotiations of this year happened on Monday between the employer and its two unions.
Recently though, GDL chief Claus Weselsky has sought to appear less antagonistic, saying at the weekend that "you shouldn't constantly brandish the threat of strikes".