Background: Pulsed electromagnetic field (PEMF) therapy, an often-used supplementary treatment in the horse industry, shows promise in enhancing circulation, reducing inflammation, and supporting cellular repair, however, its effects on equine physiology remain unclear. Limited research, inconsistent protocols, and anecdotal evidence create uncertainty about its efficacy and safety in horses. Given its growing use in equine sports medicine, further studies are needed to standardize its application. Objective: This study evaluates the short-term in vivo effects of PEMF on haematological and biochemical parameters in sport horses. Findings aim to bridge knowledge gaps and guide the safe, effective use of PEMF therapy in equine care. Study design: in vivo experiment, pilot study Methods: Five active sport horses underwent PEMF therapy (Equi Terra, model EMC-230928/1) for five consecutive days using a full-body blanket. The device was set to 1-70 Hz for 20 min., followed by 8 Hz for 15 min. Horses maintained regular training (30-40 min. daily), had ad libitum water access, and a three-meal daily routine. Blood samples were collected pre- and post-treatment to assess 72 haematological, biochemical, and endocrine parameters. Results: Pre- and post-treatment data for each parameter were analysed and compared. While most haematological parameters remained stable, significant alterations were observed in reticulocyte and platelet parameters and haemoglobin levels. Blood biochemistry exhibited greater variability, with notable changes in plasma proteins, bilirubin, uric acid, creatine kinase, creatinine, liver enzymes, and iron-binding capacity. No significant changes were observed in cortisol or thyroxine levels. Conclusion: Whole-body PEMF therapy showed no adverse effects on health or stress response. While most parameters remained unchanged, significant biochemical and haematological changes indicated enhanced physical condition, particularly in muscle function, circulation, and metabolism. These findings suggest that PEMF may support training and warrant further research on its mechanisms and applications.