The line between Manchester and Sheffield gives direct access to popular outdoor stops like Grindleford, Hathersage, Bamford, Hope and Edale.
Services are normally operated with three-carriages, but at weekends several will now become six carriage trains, doubling the number of seats in each direction.
The news follows the announcement in March that Northern had signed a deal with Marketing Peak District & Derbyshire to become one of its new strategic partners.
Chris Jackson, regional director at Northern, said: “Northern is committed to working with partner organisations to promote tourism in the Peak District and Derbyshire.
“We want to help increase the value of the area’s visitor economy and raise its profile as a world-class visitor destination – and the more cars we can take off the road as part of that project the better.”
Jo Dilley, managing director of Marketing Peak District & Derbyshire, said: “We’re delighted that our strategic partners at Northern are increasing capacity on services through the Hope Valley for the coming summer season, offering easy car-free access to some of the Peak District’s best-loved places.
“Having increased capacity not only helps to lessen the impact of cars in these sensitive locations, reducing congestion and pollution, it also opens up possibilities for walkers being able to use them to enjoy circular routes, helping us develop more active travel choices for everyone to enjoy."
Northern operates more than 2,000 services a day to more than 540 stations across the North of England.