KiwiRail said it would welcome families and holidaymakers aboard the scenic ride from 4 July.
KiwiRail chief executive Greg Miller said the TranzAlpine service was vital for the West Coast economy.
"We're conscious of how important this service is to the West Coast economy and we're looking forward to bringing visitors to the Coast again, allowing them to see the snow-capped Southern Alps along the way."
With its last ride on 22 March, Miller said the service which relied heavily on overseas tourists would need local support.
"This will be an ideal time for New Zealand families to try something new," he said.
"Covid-19 has taken a heavy toll on tourism everywhere and unfortunately, like other tourism providers, KiwiRail and the communities we serve have suffered the impact."
Lonely Planet has described it as one of the world's 10 most amazing rail journeys.
During July and August, the TranzAlpine will run on weekends, departing Christchurch at 8.15am, and spending an hour in Greymouth before leaving at 2.05pm on Saturdays and Sundays.
It will also run every day of the school holidays, 6-17 July, on the same timetable as weekends. All fares will be changeable, fully refundable and available at the winter special rate of $75 per seat one way.
The company also operates the Coastal Pacific train between Picton and Christchurch, which does not run during winter, and the Northern Explorer between Auckland and Wellington, which is not currently considered financially viable.
No decisions have yet been made on the return of the Northern Explorer and Coastal Pacific. KiwiRail also runs a commuter rail service between Palmerston North and Wellington, which resumed in late April.
