The demolition of the Thorpe Park Estate in the 1930s resulted in the grounds being converted into a gravel pit, originally owned by Ready Mixed Concrete Limited. RMC extracted gravel from the site for thirty years, from 1941 until 1970, at which point the company began planning to flood the expended gravel pits and develop the site into a leisure-based visitor attraction. In 1975, the Water Ski World Championships were held on the lake.

RMC established a subsidiary, Leisure Sport Limited, to operate the 400-acre (160 ha) park for water sports, leisure activities, and heritage exhibitions, at a cost of £3 million. The park was formally opened to the public by Lord Louis Mountbatten on 24 May 1979, in what would be his final public appearance before he was assassinated later that year by a bomb planted by the Provisional IRA on a fishing boat in Mullaghmore, Ireland. In addition to its lakes and parkland, the site featured a replica Stone Age cave, a Celtic farm, a Norman castle, and a Viking camp, as well as exhibits of historic watercraft and aircraft.

In the early 1980s, the park was redeveloped into a theme park with permanent themed rides and attractions. New large attractions were introduced throughout the 1980s, including Magic Mill, Phantom Fantasia, Thunder River, Logger's Leap and the Canada Creek Railway, along with the development of a central area of themed streets, shops and eateries.

Space Station Zero was the park's first roller coaster, an indoor powered coaster, opened in 1984.

New themed areas opened in the 1990s with Fantasy Reef and Ranger County. The last major attraction developed under Leisure Sport Ltd was the themed indoor roller coaster, X:\ No Way Out, in 1996 (now The Walking Dead: The Ride).

Between 1983 and 1989, the park was also used as a filming location for The Benny Hill Show.

In 1998, The Tussauds Group purchased the park. This period saw considerable investment, with major attractions opening such as Tidal Wave in 2000, Vortex in 2001, Colossus in 2002, Nemesis Inferno in 2003, and Stealth in 2006.

In May 2007, the Blackstone Group purchased The Tussauds Group for US$1.9 billion, and the company was merged into Merlin Entertainments, who took over operation of Thorpe Park. Dubai International Capital also acquired a 20% stake in Merlin Entertainments.

On 17 July 2007, as part of the financing for the Tussauds acquisition, Merlin sold Thorpe Park to the private investment firm Prestbury under a sale-and-leaseback agreement. The site is operated by Merlin under a renewable 35-year lease. As of 2023, the site is owned by LXi REIT plc.

In 2009, the park opened Saw – The Ride.

In 2010, the park outlined a five-year development plan, which proposed new roller coasters for 2012; this was later realised with the opening of The Swarm. The plan also included a roller coaster scheduled for 2015 and a permanent lakeside hotel, neither of which has come to fruition. No application was ever submitted for the 2015 development, and the site behind The Swarm remains undeveloped.

In 2014, Merlin also sought to broaden the park's appeal to families with additions including Angry Birds Land and the park's onsite hotel.

In July 2016, the park opened Derren Brown's Ghost Train. After the 2022 operating season, the ride’s virtual reality elements were removed, and its association with Derren Brown was discontinued.

On 20 February 2019, Thorpe Park's official Twitter account confirmed the permanent closure of Logger's Leap. In 2021, the park announced plans to construct a new roller coaster on the former site of the log flume. During the 2023 Fright Nights event, the ride was officially revealed as Hyperia. Designed to become the tallest and fastest roller coaster in the United Kingdom, Hyperia reaches a height of 236 feet (71.9 metres) and achieves speeds of up to 81 mph (130 km/h). The roller coaster opened to the public on 23 May 2024.

For the 2023 season, Derren Brown's Ghost Train was re-imagined into Ghost Train.

For the 2024 season, Thorpe Park adopted a new logo and branding, which the park stated was to "encapsulate the spirit of Thorpe Park".

For the 2026 season, it was announced that approximately half of the Amity Beach area would be redeveloped to create a new relaxation zone called The Launchpad. The Launchpad is designed as a year-round space for visitors to rest and refuel between rides, featuring seating and canopies. The smaller remaining half of Amity Beach will remain operational.

On 12 March 2026, the park released an official statement alongside Jack Silkstone, confirming the permanent closure of Rumba Rapids after 39 years of operation. The park has stated ‘Whilst we don’t have plans to share just yet on what’s next, we’re always reviewing our line-up of world-class rides and attractions to make sure Thorpe Park remains the UK’s most thrilling theme park’.