Sarco‐endoplasmic reticulum (S‐ER) stress results from physiological and pathological disturbances that alter S‐ER function. In turn, the unfolded protein response (UPR) and ubiquitin proteasome pathway (UPP) are activated in order to re‐establish S‐ER homeostasis and promote cellular resilience in the face of future cellular stressors. Unaccustomed, vigorous exercise (e.g. aerobic or resistance exercise) has been shown in the comparative mammalian literature to activate the UPR in skeletal muscle. As such, the S‐ER may play a crucial role in the adaptations of skeletal muscle to exercise. The horse represents a highly athletic and muscular mammal, yet no such research has been conducted in the horse. Eight (n=4 males, n=4 females; 3–8 yrs) unconditioned Standardbred horses completed a bout of high‐intensity fatiguing exercise in the form of a graded exercise test to determine the effects of exercise on UPR and UPP‐related markers in skeletal muscle. Biopsies were taken from the M. gluteus medius before, and at 3 h and 24 h post‐exercise, alongside time‐matched standing controls. Results showed that acute fatiguing exercise significantly increased phosphorylated eukaryotic initiation factor 2‐alpha (p<0.05) and tended to increase activating transcription factor 4 gene expression (p=0.096), but had no effect on additional UPR (e.g. Xbp‐1, Chop, Bip) or UPP (e.g. Fbxo32, Trim63)‐related mRNA transcripts. These results suggest that high‐intensity fatiguing exercise can alter UPR‐related signaling but does not induce a full transcriptional UPR or UPP in equine skeletal muscle at the time points measured.