Context: In this thesis we considered Knowledge Transfer (KT) in Global Software Development (GSD) from both the state of art and state of practice, in order to identify what are the challenges that hamper the success of KT in global software teams, as well as to find out what are the mitigation strategies that can be practiced to overcome these challenges. Objectives: The main objective of this research is to find an in-depth understanding of knowledge transfer challenges and mitigation strategies from both literature studies and industrial experienced employees. It also identifies the similarities and differences of challenges and strategies from literature studies and industrial experienced employees. The overall aim of this work is to provide a list of mitigation strategies to challenges, as guidelines to enable successful knowledge transfer in GSD. Methods: In order to fulfill the aim of the research, we collected the data through a Systematic Literature Review (SLR) and industrial interviews. Through SLR we found 35 articles relevant to our objectives. The data is extracted from those articles and conclusions are drawn. The relevant data is collected from databases such as Engineering village, ACM Digital Library, Science Direct, Wiley Inter Science, Scopus, ISI Web of Science and IEEE Xplore. We conducted 8 interviews from 8 different multinational companies. For analyzing the data we used grounded theory and qualitative comparative analysis. Results: In total, 72 different challenges and 107 mitigation strategies were identified from both SLR and interview results. In most of the studies, KT challenges in GSD are categorized into 3Cs (Communication, Control and Coordination). We also came up with a different view known as 2PT which conceptualizes the KT challenges and strategies into Personnel, Project and Technology factors. Conclusions: In future, researchers have to focus on the personnel, project and technology factors for implementing an effective KT process. From a practitioner‘s view, the results can be used to identify critical factors for effective KT. The challenges to KT show to what extent these results can be industrially applicable.