The company's legal headquarters have been located at the offices on Calle Juan Esplandiú in Madrid since October 2017 due to the 2017–2018 Spanish constitutional crisis.

In 2005, the deployment of Digital Terrestrial Television began in Spain, with a network that reached 80% population coverage carrying out the first tests in Madrid, Barcelona, Valencia, Zaragoza and Gijón.

In 2014, it acquired TowerCo, an Italian telecommunications operator, which manages the mobile phone towers located in the entire motorway network of Italy, thus initiating the process of internationalization.

[11] With the IPO of Cellnex Telecom, Abertis fulfilled one of the main objectives of the Strategic Plan 2015–2017, with which it intended to value its telecommunications business and obtain resources to invest in growth and international expansion of its highway division.

Cellnex Telecom is present in four different areas: The company has thousands of mobile phone towers, being the first independent European operator in the management of telecommunications infrastructures.

Cellnex Telecom is specialized in the deployment of networks prepared for 5G technology because of its presence in twelve European countries: Spain, Italy, the Netherlands, France, the United Kingdom, Switzerland, Ireland, Austria, Denmark, Portugal, Sweden and Poland.

In addition, in May 2019, the company announced a new agreement with Iliad France with which it will manage the sites that are currently integrated into Free, a French voice and data operator.

The main customers interested in telecom infrastructure services are the Dutch mobile network operators KPN, Vodafone, T-Mobile and Tele2.

The agreement follows the announcement in June 2020 of a long-term strategic alliance with BT, through which Cellnex obtained the rights to commercialize and operate 220 high-rise towers distributed throughout the United Kingdom.

In September 2019, Cellnex reached an agreement with InfraVia Capital Partners for the acquisition of the Irish telecommunications tower and site operator Cignal.

In March 2024, it was announced Cellnex Ireland had been acquired by the Boca Raton, Florida-headquartered wireless infrastructure operator, Phoenix Tower International for €971 million.