The nucleus of the Theory Group was a four-man team comprising N. Bohr, C. Møller, J. Jacobsen, and S. Rozental. It was founded in May 1952, and was initially located in the Theoretical Physics Institute at the University of Copenhagen.

The first theorists came to Geneva in 1954, and were based first at the University of Geneva, then in barracks at the airport. The work of the group included:

Scientific research on fundamental problems of nuclear physics, including theoretical problems related to the focusing of ion beams in high energy accelerators.

Training of young theoretical physicists.

Development of active co-operation with the laboratories of Liverpool and Uppsala, whose machines and equipment had been placed at the disposal of CERN.

In 1954 the CERN Theoretical Study Division was set up. The rest of Copenhagen group moved to Meyrin at CERN in 1957.

In 1960 as the PS research experimental programme began, CERN had to adapt its internal structure to its changing tasks. The original six divisions were reorganized into twelve divisions. The role of Theoretical Studies (TH) Division was: theoretical physics research, and co-operation in the preparation of experimental programme and in the interpretation of the experimental results.

In 1966 new departments, which remained until 1976 were formed by regrouping the existing divisions. The Theoretical Studies Division was integrated into the Theoretical Physics Department.

In 1971 following approval for the construction of a second Laboratory adjoining the existing site, CERN was divided between two administrative units, Laboratory I and Laboratory II. TH Department was part of Laboratory I.

In 1976 the two Laboratories were united. The departmental structure ceased and Theoretical Physics Department was renamed Theoretical Physics Division (TH).

In 1986 the Scientific Information Service (SIS: Library and Archive), formely part of DOC Department, was added to the TH Division.

In 1990 the SIS Group moved in the new Administrative Support Division (AS).

In 2016, the CERN management changed and adopted a new organizational structure.  The Physics Department (PH) was split into two separate departments: Experimental Physics Department (EP) and Theoretical Physics Department (TH) located with the Information Technology Department (IT) in the Research and Computing Sector (RC).

The TH Department carried out research on all subjects of relevance for theoretical particle physics: QCD, electroweak theory, collider phenomenology, physics beyond the standard Model, heavy ions, flavour physics, neutrino physics, lattice field theory, formal aspects of quantum field theory, string theory, cosmology, and astroparticle.