Support spaces in shopping centers (playgrounds, food court and the like) were first created to serve the booming of the business in such centers. But, they gradually were turned to direct destinations for human activities meaning that the visitors, having no intention to buy, spend some of their leisure time in these shopping centers for such purposes as amusement and social interaction and so on and, in fact, a sort of novel public space is formed in the business centers. It seems that the main reason why these places have been transformed is their livability. Thus, the present study’s primary hypothesis is that “the newly-formed public support spaces are lively and this livability causes functional shifting of these spaces from dependency on active spaces to semi-public urban spaces”. The present study aims to identify, within the format of a conceptual model, the factors contributing to livability in the support spaces of the business centers. The present study is a qualitative survey and, in line with this, after performing documentary research and reviewing the relevant experiences, the related concepts were, in the first step,  extracted in the form of livability aspects and variables; then, in a second step, in the survey study stage, five commercial blocks, as examples of more successful complexes in terms of livability and attraction of the visitors, not business clients, to spend their leisure time in their support spaces were selected according to the geographical scattering diversity in Tehran. Next, observations and deep interviews were carried out for each of the case samples to extract the aforementioned variables giving rise to support spaces’ livability. The results of the study indicated that there are two major branches for the livability of the support urban spaces in the modern commercial buildings: convenience and semi-public nature of them. Thus, the collection of the effective indicators was offered within the format of a conceptual model to assess livability of the modern commercial blocks’ support spaces. The study hypothesis was approved according to a qualitative analysis undertaken in the survey research based on the functional independence of such spaces in modern commercial buildings. Finally, the questions raised herein were answered and suggestions were made regarding the methods of enhancing livability of the support spaces in such public spaces.