Objective: To study if computerized working memory (WM) training, in the sub-acute phase after acquired brain injury, in patients with impaired WM, improves WM, cognition and psychological health. Research design: A randomized study (n = 47) with an intervention group (IG) and a control group (CG), mean age 47.7 years. The WAIS-III NI, Digit span, Arithmetic, Letter-Number Sequences (Working Memory sub-scale), Spatial span, the Barrow Neurological Institute Screen for Higher Cerebral Functions (BNIS) and the self-rating scales DEX and HADS were administered at baseline and at follow-ups at 6 and 18 weeks. Both groups underwent integrated rehabilitation. The IG also trained with the computerized WM training program, Cogmed QM, which was offered to the CG and followed up after the study completion. Results: Both groups improved after their WM training in Working Memory, BNIS and in Digit span, particularly the reversed section. Both the BNIS and the Digit span differed significantly between the IG and CG due to the greater improvement in the IG after their WM training. Psychological health improved as both groups reported less depressive symptoms and the CG also less anxiety, after the training. Conclusion: Results indicated that computerized WM training can improve working memory, cognition and psychological health.