The overarching purpose of this thesis is to develop further knowledge of the consequences of relocating to Activity-based Flexible Offices (AFOs). As workspace design innovations, AFOs are increasingly implemented in organisations. AFOs comprise a variety of workspaces for employees to choose from depending on their preferences or activities. Workspaces in AFOs are shared, instead of every employee having their own desk. Research results are inconsistent regarding employee satisfaction with AFOs, and research into employees’ appropriation of AFOs and organisations’ processes of adopting AFOs is sparse. In response to these knowledge gaps, the thesis aims to explain why some AFOs work while others do not. The thesis builds on five case studies: (i) three cases with recently implemented AFOs, and (ii) two cases with AFOs implemented at least two years prior to the study. Data collection in all the case studies involved semi-structured interviews with employees and facility managers, observations and collection of secondary data such as process overviews, and layout drawings. For data collection and analysis, a theoretical framework was developed and used consisting of Activity Theory, artefact ecology, as well as theories of innovation adoption and appropriation. The findings show that individuals’ usage of AFOs varies considerably due to personal circumstances and work-related preconditions. Drawing on Activity Theory, three types of matches/mismatches were identified in employees’ activity systems: Employee ↔ AFO, Activity ↔ AFO, and Employee ↔ Activity. Furthermore, individuals’ usage preferences and non-preferences highlighted sub-optimal design features in the AFOs: (a) ambiguity and insufficient communication of rules; (b) undesirable ambient features; (c) exposure to stimuli; (d) difficult to interpret workspaces; and (e) dysfunctionality and insufficiency of the collective instruments. In summary, AFOs work in the absence of mismatches related to individuals’ personal and work-related preconditions and sub-optimal design features. The employees’ processes of appropriating AFOs involved first encounters, exploration, and stable phases, during which various types of adaptations occurred: (i) on an individual level: acquired insights, and behavioural, social and hedonic adaptations, as well as (ii) in the AFO solutions: rule-related, spatial and instrument adaptations. Furthermore, the AFO adoption process in organisations varied considerably.\ua0 Procedural shortcomings during the planning process led to a limited understanding of AFO users and thus the sub-optimal AFO designs, while shortcomings during the routinising stage involved restrictions on making post-relocation improvements in AFOs and inadequate Occupational Health & Safety management. To conclude, AFOs work provided (i) they match individuals’ personal circumstances and work-related preconditions; (ii) they facilitate flexibility and shared use of spaces through well-designed rules, workspaces and instruments; (iii) individuals’ appropriation processes reach a stable phase where mismatches are resolved and fruitful symbiosis is achieved in their activity systems; and (iv) the organisations’ process of adopting AFOs is successful both during the planning and the post-relocation routinising stages, leading to a collective sense of ownership among employees