This study evaluated heat tolerance and biochemical and haematological responses of Holstein cows exposed to different environmental conditions (full sun or shade) and feeding regimens (with or without concentrate) in the semi-arid region of Brazil. Sixteen adult cows were distributed across four treatments. Rectal temperature increased in sun-exposed cows from an average of 38.0 degrees C (8:00 a.m.) to 38.6 degrees C in the afternoon, reaching a maximum of 40.0 degrees C in the sun + concentrate treatment. Respiratory frequency was highest in sun + concentrate conditions at 12:00 p.m. (average 70.0 bpm; maximum 100 bpm). Heat tolerance index was highest in sun + concentrate conditions (average 4.0-3.7; maximum 5.4). Average daily gain was positive only for shaded cows, reaching 0.60 kg/day (with concentrate) and -0.41 kg/day (without), while sun-exposed animals lost weight (-2.37 and -3.41 kg/day). Cholesterol was lowest in cows under the sun without concentrate (55.41 mg/dL). Shaded cows receiving concentrate had increased red blood cell counts (6.65 million/mm3), but lower hemoglobin (11.99 g/dL), hematocrit (36.0%), mean corpuscular volume (54.27 fL), and mean corpuscular hemoglobin (18.08 pg). Overall, shade combined with concentrate resulted in better heat tolerance, improved weight gain, and more s metabolic and haematological profiles compared to full-sun exposure.