Wellington trains will be replaced by buses between 9am and 3pm on Thursday as rail workers attend a union meeting.
Wairarapa trains are already replaced by buses due to maintenance, and with Transdev staff in the annual meeting, the Hutt Valley, Melling, Johnsonville, and Kapiti lines will also be affected.
Metlink general manager Samantha Gain said people should allow extra time for their journeys.
"We will keep customers updated through our website, mobile phone app and social media channels," she said.
Scheduled bus replacements running before 9am and after 3pm on Thursday will run as normal, Gain added.
Pink bus replacement posters will be displayed at train stations.