Despite the development of various frameworks to assist in the appraisal and selection of government projects, failures are still being recorded with government projects. In developing countries, where frameworks are rarely used, the problems are compounded. To improve the situation this study investigates the current practice of construction project selection processes within the Nigerian public sector in order to inform theories of decision making from the perspective of developing nations and project management practice. The study adopts approach that challenges the concepts of conventional scholars. More specifically, it adopts Activity Theory concepts in the development of a conceptual framework. Data were collected through semi-structured interviews with a purposeful sample of 30 senior public sector management personnel within the five parallel case organisations between March 2015 and November 2017. The data obtained from the interviews were then compiled and analysed using qualitative software for content analysis. Using activity theory as the basis of the investigation, the findings identified a number of artefacts mediating project selection activity. Findings revealed that with the increase in population, incidence of infrastructure shortage has continued to increase in Nigeria, causing a severe challenge, especially to the Nigerian government. The citizens now depend largely on dilapidated and/or in some instances on low quality infrastructure and feel strongly that the shortage in infrastructure supply capacity and the rate of marginalisation of some regions in the provision of infrastructure is pushing the country towards disaster. This feeling is compounded by the fact that the majority of government projects have not delivered the anticipated benefits within time and cost expectations. A number of factors were identified as influencing the project selection process within the public sector and these have been grouped under six categories: technical factors, stakeholders’ expectation factors, financial feasibility factors, social factors, strategic alignment factors and external factors. Findings emerging from this study reveal that a visible theoretical project selection framework to support public sector decision makers in making project decisions is still lacking. The thesis concludes by proposing a selection framework and guidelines/protocols that will aid decision makers to be consistent in assessing and selecting construction projects within the Nigerian public sector. The results from this study also indicate that the level of stakeholder participation is still low. This study supports positive stakeholder engagement by informing decision-maker the need to adopt bottom-up approach where stakeholders drive the project selection process rather than the top-down approach where the executive drives project selection process as is currently the practice in Nigeria.