The study aimed to investigate the effect of fatigue on static and dynamic postural control after finishing a mountain ultra-marathon race. Twelve male athletes participated at the study. Postural stability was assessed before and immediately after the race. Bipodalic standing balance was measured on a dynamometric platform with eyes opened (OE) and closed (CE). Dynamic test was performed with OE on an instrumented plate which allowed medio-lateral oscillations. Stabilometric data were affected by fatigue in the OE condition, concerning sway path (p=0.0006), sway area (p=0.0006), area of the confidence ellipse (p=0.0016), maximal AP (p=0.0017) and ML (p=0.0039) oscillations. In the CE condition the sway path (p=0.0334), the maximal ML oscillations (p=0.0161) and the area of the confident ellipse (p=0.0180) were also negatively influenced. Stabilogram diffusion analysis showed in the OE condition an increase of short-term diffusion coefficients considering the anterior-posterior direction (Dfys; p=0.0023) and the combination of the two directions (Dfr2s; p=0.0032). Equally, long term diffusion coefficients increased considering the anterior-posterior direction (Dfyl; p=0.0093) and the combination of the two (Dfr2l; p=0.0086). In CE condition greater values were detected for medio-lateral (Dfxl; p=0.033), anterior-posterior (Dfyl; p=0.0459) and the combination of the two (Dfr2l; p=0.0048). Dynamic test showed an increase of the time spent with the edges of the plate on the floor (p=0.0152). These results suggest a more marked involvement of cognitive resources to monitor postural stability after fatiguing. This caused a worsening in the automatic task (quiet standing) and a positive compensation in the less automatic task (dynamic test).