Alton Towers first opened to the public on a regular basis following the opening of Alton Towers railway station. Money raised from railway excursions was paid to the earl and helped to maintain the upkeep of the grounds.

In 1924, a group of local estate agents formed Alton Towers Ltd to take ownership of the estate and began to restore the gardens as a tourist attraction. In the 1950s, this included the operation of a fairground, and by the 1970s included a boating lake and chairlift.

Property developer John Broome purchased a majority stake in the park after marrying the daughter of majority shareholder Dennis Bagshaw in 1972. From there, he began the theme park by developing new areas and installing permanent rides, including the Corkscrew, The Flume, Around The World in 80 Days, The Black Hole and the Grand Canyon Rapids.

In 1990, Broome sold Alton Towers to The Tussauds Group, then a division of Pearson plc, after his development of the former Battersea Power Station encountered financial difficulties. The change of park ownership brought another era of development, involving the opening of new themed areas and attractions, such as Runaway Mine Train (1992), The Haunted House (1992), Toyland Tours (1994), and Nemesis (1994). The Thunderlooper opened in 1990, but closed in 1996 due to complaints about the noise and height of the ride. Tussauds' park development team from 1990 to 2002 included attraction producer John Wardley among others.

The Tussauds Group was sold to venture capital firm Charterhouse in 1998. The opening of Oblivion that same year and Air (now Galactica) in 2002 saw the park sustain new major roller coasters, both marketed as 'World First' rides. In 2005, Dubai International Capital (DIC) acquired Tussauds for £800 million.

2004 saw the opening of Spinball Whizzer. In 2005, Rita opened in the Ug Land area of the park. It was the first major roller coaster addition since the Thunderlooper to not use the Secret Weapon project name, instead using the same name as the final ride.

In May 2007, The Blackstone Group purchased The Tussauds Group for US$1.9 billion and merged it with its then-subsidiary Merlin Entertainments. Dubai International Capital also gained 20% of Merlin Entertainment.

On 17 July 2007, Alton Towers was sold to private investment firm Prestbury under a sale and leaseback agreement. Merlin continues to operate the site under a renewable 35-year lease. As of 2023, the property is owned by LXi REIT plc.

As of early 2008, the resort changed its name to Alton Towers Resort to better reflect its status as a multi-day destination. Most other Merlin-owned theme parks with onsite accommodation would follow soon afterwards. In this year, the Corkscrew closed to make way for the next major addition. The corkscrew element was later placed at the front of the park, along with a memorial.

For 2010, Merlin brought back the "Secret Weapon" project name with TH13TEEN, opening in March of that year, and built on the former site of the Corkscrew. This was the first ride to feature a drop track, manufactured by Intamin.

In 2020, Alton Towers operated on a shortened season due to the COVID-19 pandemic, operating on a limited capacity from 4 July to 5 November. The resort resumed normal operations on 12 April 2021.

30 years after originally opening, 2024 saw the introduction of Nemesis Reborn. After the majority of the original track and supports were removed in 2022, and then reconstructed using brand new track, it reopened on the 16th March 2024. The new ride also included a complete overhaul of the Forbidden Valley area, including a brand new shop, arcade, and the Phalanx having a much larger presence. New theming features were added throughout the area, such as a brand new helicopter outside the entrance, and a new gun feature added inside the queue. The most notable addition was the screen-based eye on the side of the station. 2024 also saw a brand new event, Alton After Dark. This took place on the 16th, 23rd and 30th of March, with the park close extended until 8pm. This event was brought back in 2025, with more dates added.

2025 saw the opening of Toxicator in Forbidden Valley, a brand new HUSS suspended topspin, on the 15th of March. It is located on the former site of Ripsaw. 2025 also saw a cut to entertainment offerings, with the main stage on the lawn being removed, and roaming actors no longer appearing.