Background: Poststroke fatigue (PSF) is a form of pathological fatigue that can develop after stroke and has a negative impact on functional outcome. PSF is associated with poststroke depression (PSD), which in turn shows similarities with poststroke apathy (PSA). This study aimed at disentangling the temporal associations between PSF and PSD and between PSF and PSA. Methods: A total of 250 stroke patients were included, of which 243 completed the Fatigue Severity Scale, Montgomery-Åsberg Depression Rating Scale, and Apathy Evaluation Scale at 3 months poststroke, with follow-up measurements at 6 and 12 months after initial testing. Linear mixed models and linear regressions were performed to evaluate the temporal associations between PSF and PSD, and between PSF and PSA. Results: PSF was present in 119 patients (49%), of whom 62 patients also had PSD (26%), and 21 patients (9%) also had PSA. At baseline, PSF patients showed higher depression levels, which remained stable at follow-up. PSD patients had higher fatigue levels compared with no-PSD patients at baseline, which remained stable at follow-up. No association between apathy and fatigue was found at baseline and no interaction with time was found. Change in fatigue from baseline to 12-month follow-up was associated with change in depression and with change in apathy. Conclusions: Bidirectional associations were found between PSF and PSD. In treatment and rehabilitation programs, early focus on the presence of PSD and PSF is important, since these conditions tend to persist. As there are currently more treatment options for PSD, attention for PSD is important and might also have a beneficial effect on PSF.