Large-scale distributed software projects with long life cycles often involve a considerable amount of complex legacy code. The combination of scale and distribution challenges and the difficulty in acquiring knowledge about massive amounts of complex legacy code may make the onboarding of new developers/teams problematic. These problems may lead to extended periods of low performance. The primary objective of this paper is to investigate the performance evolution of offshore newcomers onboarded in a large-scale globally distributed project and how it relates to the employed onboarding strategy. To achieve our objective, we conducted a case study in Ericsson. We identified that the following aspects in the onboarding strategy employed in the investigated case seem to be related to the unexpectedly low performance evolution: i) the distance to mentors; ii) the used formal training approach, which did not fit the sociocultural background of the newcomers; iii) allocation of large and distributed tasks in the early stages of the onboarding process; and iv) team instability. We conclude that the onboarding of newcomers in globally distributed projects must be planned well ahead and should consider avoiding the aspects mentioned above. © 2019 IEEE.