Purpose: This study aims to investigate how the processes of memory acquisition, retention, retrieval and application occur in project-based organizations (PBOs). In this kind of organization, the nature of corporate memory is influenced by the transience, uniqueness and independence of the project portfolio. Such understanding may help practitioners to mitigate the effects of project transience and promote knowledge sharing among project teams. Design/methodology/approach: An empirical and qualitative study was carried out through a multiple case study approach conducted in three Brazilian Engineering Design Firms, which are organized by projects. Document analysis, direct observation and semi-structured interviews with engineers, project managers and executives were conducted. Findings: The memory acquisition process takes place in five forms which have different sources and destinations when comparing PBOs with traditional organizational settings. Memory retention in PBOs crosses organizational boundaries and establishes a knowledge network of former employees and third parties. The PBOs project memory can be divided into volatile and perennial memory, where the former can be lost throughout project execution and the latter is internalized, becoming an inseparable part of the corporate memory. Memory retrieval in PBOs is also distinct since it has particular mechanisms depending on whether the knowledge is technical or administrative. Originality/value: The research investigates the corporate memory processes within the volatile context of PBOs in a Latin-American developing country whose culture favors tacit knowledge exchange. The paper proposes a framework that unveils different patterns of knowledge acquisition, temporary and perennial retention structures, intensive usage of external knowledge in memory retrieval and particular memory applications in PBOs. The framework may guide scholars, project managers, engineers and practitioners in navigating through the uniqueness of organizational learning flows and structures in PBOs.