Despite the spread of Public-Private Partnerships (PPPs) and their interest among academicians and policy-makers, many investigations generally treat them as a homogenous mode of governance neglecting their different forms. The present work investigates the factors that determine the concrete form of PPP finally adopted. We use the Transaction Costs Theory (TCT) to analyse 11,821 PPPs in 110 developing countries from 1997 to 2017. The results show that the greater the amount of specific investment and the more unfavourable the context in which it is implemented, PPP adopts forms where the private party has a greater degree of control.