Purpose -To investigate what actually influences a merger and acquisitions (M&As) successful implementation. Despite the significant research interest in this topic our knowledge is still incomplete. Design/methodology/approach -Our approach differs from traditional research efforts in the field. First, it explores the influence of a range of factors including external corporate environment, company characteristics, communication program and the characteristics of the M&A itself. Second, it is based on a comparatively large sample of 72 in-depth studied M&As which took place in Greece. Findings -Results indicate that the existence of a communication program is among the most influential factors in the successful implementation of an M&A. Other determining factors are aspects of the external corporate environment, the formalization of the decision-making process and the consequentiality of the M&A. Research limitations/implications -More empirical studies are needed to replicate and extend our study by examining variables not included here. Moreover, it would be particularly interesting to conduct similar studies in other countries, where the M&A practice is still young (i.e. newly accepted EU countries). Practical implications -Results show that the appropriate communications strategy is the area that can significantly improve the odds of success in post-merger integration. In addition, our findings might be of importance to newly accepted EU member countries as they are likely to attract a wave of M&As in the coming years. Originality/value -The paper explores a range of factors and investigates their effect on the successful implementation of M&As. Few studies have empirically examined such a combination of factors on M&A success using a relatively large sample of acquisitions.