Aims: We hypothesised that a systematic functional assessment in a short stay unit at an emergency department (ED) and/or immediate rehabilitation after discharge will result in sustained or improved physical performance in comparison to a regimen in which neither of these interventions is offered. Methods: A two-way factorial randomised clinical trial was completed in an ED and the primary sector. We enrolled 336 nonsurgical patients of 65 years or older, scoring eight or less in the 30-s chair stand test. The interventions were: 1) Usual assessment; 2) Usual rehabilitation; 3) A systematic functional assessment performed within 48 h of admission, in order to identify those with loss of functional mobility, or at risk thereof; and 4) Immediate rehabilitation initiated within five days after discharge. The primary outcome was the 30-s chair stand test three weeks after admission. Secondary outcome measures were Barthel, EQ-5D-3L, and length of stay (LOS). Results: An intention-to-treat analysis showed no significant difference in the 30-s chair stand test score nor when analysed by groups or by intervention. The changes were approximately 1% when compared to the reference. No significant differences were found in the secondary outcomes. A per-protocol analysis showed that 99% had received assessment as assigned; however, the extent of mobilisation during hospitalisation was not disclosed. Of the patients, 48% were received the post-discharge rehabilitation they were assigned to. Conclusions: Systematic functional assessment and immediate rehabilitation led to no significant differences in physical performance. The study was weakened by the incomplete implementation of mobilisation during hospitalisation and low adherence to protocol on immediate rehabilitation.Implications for rehabilitation A systematic functional assessment within the first 48 h of hospital admission is suitable for the identification of older adults in need of post-discharge rehabilitation when compared to usual assessment. To sustain physical performance in older adults during acute hospitalisation, further research focusing on mobilisation or physical activation is needed in older adults with a loss of functional mobility, or at risk thereof. Further research focusing on physical activation during transition is needed to ameliorate tiredness and inactivity in older adults after acute hospitalisation.