Background: Approximately 10%-15% of people diagnosed with a concussion develop post-concussion syndrome (PCS), in which mental fatigue is a dominating symptom. PCS has major consequences for the individuals diagnosed, and society as a whole. Objective: The objective of the pilot study was to investigate whether a nature-based therapeutic (NBT) intervention would be suitable for ameliorating the symptoms experienced by people with PCS, especially mental fatigue. Method: Eight participants diagnosed with PCS took part in a NBT programme, which consisted of weekly two-hour sessions over the course of eight weeks. The participants' level of mental fatigue was measured on the Mental Fatigue Scale (MFS) before and after the intervention. An analogue scale inspired by the EuroQol-visual analogue scales (EQ-VAS) was used to measure immediate self-perceived feeling of health/ well-being before and after individual sessions. A semi-structured interview was held with each participant after the intervention. The interviews and logbooks were analysed through content analysis, which entails several steps in a spiral-like process, from reading and re-reading the transcripts to forming units of meaning, which were then grouped into sub-categories and categories for further analysis. Result: The MFS showed a significant decrease in mental fatigue and large effect size. The participants' self-assessed health/ well-being on the analogue scale showed an increase from the beginning to the end of each session. The analysis of the interviews revealed that the participants experienced the sensory stimuli and exercises in the natural environment as motivating and meaningful, even when they were challenging. Further, they found the psycho-educational aspects transferable to everyday life. Conclusion: The results support that NBT can have potential in the rehabilitation of PCS, by lowering mental fatigue and improving health