Background: Postprandial falls in blood pressure (BP) are more common in older compared to younger individuals. The effects of protein compared to carbohydrates and fat on postprandial BP, and the relation to gastric emptying rates, are poorly studied. Objectives: To determine the effects of a whey protein compared to a control drink on systolic BP (SBP) and diastolic BP (DBP), and heart rate (HR) in healthy younger and older men, and to relate these effects to gastric emptying. Design: A pooled analyses of two randomized, double-blind, cross-over studies. Setting: Two acute clinical intervention studies with identical study design. Participants: Nineteen older (age: 74 ± 1 years, body mass index: 26 ± 1 kg/m2) and 13 younger (23 ± 1 years, 24 ± 1 kg/m2) healthy men. Intervention: A 70 g/280 kcal whey-protein or control (water with diet cordial, ~2 kcal) drink (450 ml). Measurements: BP and HR were assessed with an automated device immediately before and at 3-min intervals after drink ingestion (0–180 min). Gastric emptying of the drinks was measured using 3D ultrasonography (0–180 min). Results: Older versus younger men exhibited a greater fall in SBP (−23 ± 2 vs −15 ± 2 mmHg, p = 0.001) after whey-protein versus control, as BP did not change after the two drinks in younger men (p > 0.05). The nadir in SBP occurred later in the older than younger men (114 ± 11 vs 62 ± 14 min; p < 0.001), with SBP still apparently declining 180 min after whey-protein ingestion in the older men. The magnitude of the rise in HR was greater (p < 0.05) in the younger than older men. Conclusion: Following ingestion of 70 g whey protein, healthy older men exhibited a sustained fall in BP, despite an increase in HR, whereas in younger men there was no change in BP. BP may need to be monitored after high protein meals in older people at risk of postprandial hypotension.