Usually pinned ends are assumed to calculate the compression capacity of closely spaced double angle members. In reality the joints used in practice provide additional rotational restraints at the member’s ends, which significantly influence the compression member capacity of such built-up sections. Within this paper, back-to-back connected angle sections are studied in detail. In a first step finite element models for such members are developed and validated against experimental tests in the laboratory from literature. All available tests are only carried out for simplified support conditions, with hinged or fixed supports. Thereby, the effect of realistic end supports is generally disregarded. Therefore, the current study sets out to systematically investigate the influence of additional rotational restraints at the member’s ends, based on conventional practical joints, on the compression member capacity of built-up double angle members. This is realized by means of a numerical parametric study based on the developed finite element models, including the effect of rotational restraints at the member’s ends. The varied parameters are: i) member length, ii) type and dimension of the individual angle sections, iii) number of interconnections, iv) dimensions of the gusset plates at the member’s ends (i.e. thickness, width and depth) and, v) size of rotational restraints at the end of the gusset plates simulating the stiffness of an adjacent structure. Finally, a design model is introduced which is based on second order theory calculation of an eccentrically loaded column with rotational end restraints. Furthermore, appropriate stiffness functions for these rotational end restraints are presented. It is shown that by means of this new design model the ultimate compression capacity of closely spaced double angle members can be predicted accurately and more economical than by current design procedures.