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 to help maintain the grounds.

In 1924, a group of local estate agents formed Alton Towers Ltd to take ownership of the estate and kept the gardens open as a visitor attraction. The estate was later closed to the public upon its requisition by the military during the Second World War.

In the early 1950s, ownership was returned to Alton Towers Ltd and the grounds reopened to the public. Alton Towers continue to grow as a visitor attraction, with additions including a railway, fairground and, by the 1960s, a boating lake and chairlift. Property developer John Broome later acquired majority control in the park and began planning its development as a theme park.

Under John Broome's ownership, Alton Towers was opened as a theme park in 1980 with the introduction of a pay-one-price ticket structure and new attractions, including the Corkscrew. The following years saw new rides and areas including 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). 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. Oblivion opened that same year and Air (now Galactica) opened in 2002, both advertised as 'World First' ride types, followed by Spinball Whizzer in 2004.

In 2005, Dubai International Capital (DIC) acquired Tussauds for £800 million. That same year, Rita–Queen of Speed was built in the Ug Land area of the park.

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 2024, the property is owned by LondonMetric Property.

As of early 2008, the resort changed its name to Alton Towers Resort to better reflect its status as a multi-day destination. That year, the Corkscrew closed and its corkscrew track element was placed in the park admissions plaza as a feature. TH13TEEN, the first roller coaster to feature a freefall drop track, opened in March 2010 on the former site of the Corkscrew.

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.

In 2024, Nemesis was revamped as Nemesis Reborn after a year-long refurbishment, along with a revamp of the surrounding Forbidden Valley area. The following year saw the opening of Toxicator in the area, a HUSS suspended topspin, on the former site of Ripsaw. 2025 also saw a cut to entertainment offerings, with the stage on the lawn being removed and a decrease in live actors.