Procurement instruments by Public Private Partnerships (PPP) have shown their amazing capacity in procuring public works from around the globe. Their success rate has been immense as they are known to bring efficiency, quality, innovation, experience, funds, and most importantly, the art of risk sharing to developed projects. This research aims to pinpoint the critical success factors (CSFs) that are needed to implement PPPs in transitional economies. We have taken UAE as a case study and will be comparing its results with that of the UK's; a developed country. Relevant data was collected through a questionnaire to establish the PPP critical success factors for the each of the two countries. In this questionnaire, data was collected from 30 participants residing in the UAE and 62 participants residing in the UK. A comparative analysis between the results of the UK and UAE showed a great deal of similarity between the two in PPP practice trends in the critical success factors. Both countries ranked the same nine factors as the most significant ones out of the eighteen critical success factors for implementing PPPs. These factors were commitment of public and private parties, appropriate risk allocation, committed and competent public agency, transparent procurement process, strong private consortium, competitive procurement process, political support, detailed cost/benefits assessment, and good governance. Whereas, the major differences were related to local financial market, macro-economic conditions, and favourable legal framework. The findings were validated through a small sample of practitioners using the Partnering Performance Index, and were found to be comprehensive, objective, reliable, practical, replicable, and adaptable.