The phrase Triple Bottom Line (TBL) was first coined in 1994 in order to introduce social and environmental considerations in the traditional finance-centric measurement system of business performance. As a tool to measure sustainability performance, the three bottom lines refer to the environmental, social and economic aspects of sustainability respectively. The implementation of the TBL framework in the construction sector is considered to be insufficient due to the industry’s reluctance to change. The objective of this research is to create an assessment tool based on performance indicators that will encourage construction companies to continuously monitor and improve sustainability performance. Initially, the large scientific database Scopus is being reviewed. The literature study resulted in the identification of 71 performance indicators (24 for the environment, 24 for the society and 23 for the economy, respectively. Moreover, 13 assessment frameworks were studied, however, they fail to provide holistic, quantitative results. Thus, a new assessment methodology is developed where the initial inventory of indicators is refined according to specific criteria, weights are allocated to indicators in order to reflect their importance to the project and its stakeholders, and then, the weighted sums are calculated and plotted in spider diagrams and bar charts. The case study was employed as a research method and the purpose was twofold: Firstly, to investigate the current practices in the field of sustainability in the construction industry and, secondly, to examine the feasibility of applying the proposed assessment tool. The results confirmed the poor integration of the TBL framework in the construction industry and the suggested tool was confirmed to be comprehensive, simple and straightforward, and at the same time the results could be very easily communicated with the project’s stakeholders. The most important deficiency of the proposed model was found to be the subjectivity in the assessment procedure. For that purpose, four assessment criteria are proposed in order to limit the subjectivity inserted in the evaluation process. A conceptual framework is also proposed to help organizations adopt the assessment tool in their daily practices.