Wellingtonians are encouraged to plan ahead if they are travelling on Monday between 9.30am and 3pm, when bus and rail staff will be attending their respective union meetings.
Tranzurban bus drivers will attend a Tramways Union meeting in the Hutt Valley, while rail staff will attend a Rail and Maritime Transport Union meeting.
Metlink senior manager Matthew Chote said the disruption would be temporary, with services resuming as soon as possible.
"Off-peak rail services on all lines are to be replaced by buses between 9.30am and 3pm on Monday, while off-peak bus services in the Hutt Valley may be disrupted from late morning to 1pm," he said.
"We encourage our passengers, particularly those who live in and around the Hutt Valley, to travel earlier in the morning or later in the day to avoid any disruptions to their usual services."
The Tramways Union meeting would not affect school services, or bus services run by other operators.
The affected bus routes include: 110, 111, 112, 113, 114, 115, 120, 121, 130, 145, 149, 150, 154, 160 and 170.
"Metlink supports union members attending their meetings and expects most of Monday's services to run as usual," Chote said.
Passengers can plan ahead using the Metlink website, app, or by calling 0800 801 700 for the latest travel information.