Aim: The aim of this study was to evaluate the immediate effects of short-duration slow deep breathing on heart rate, blood pressure, respiratory rate, oxygen saturation, and heart rate variability (HRV) in healthy young adults.Materials and Methods: This prospective, randomized controlled study included 120 healthy young adults aged 20-25 years. Participants were divided into two groups: the control group (n = 60), who maintained normal breathing for 5 minutes, and the intervention group (n = 60), who performed slow deep breathing exercises for 5 minutes. Baseline and post-intervention measurements of heart rate (HR), blood pressure (BP), respiratory rate (RR), oxygen saturation (SpO2), and HRV were recorded. Statistical analysis was conducted using paired t-tests and independent t-tests.Results: The intervention group showed a significant reduction in heart rate (65 ± 7 bpm vs. 75 ± 8 bpm, p < 0.001), systolic BP (115 ± 9 mmHg vs. 120 ± 10 mmHg, p = 0.045), and diastolic BP (75 ± 7 mmHg vs. 80 ± 8 mmHg, p = 0.001). Respiratory rate also decreased significantly (12 ± 1 breaths/min vs. 16 ± 2 breaths/min, p < 0.001), and tidal volume increased (500 ± 40 mL vs. 450 ± 50 mL, p = 0.029). HRV parameters showed improvement, with higher SDNN (70 ± 12 ms vs. 50 ± 10 ms, p < 0.001) and RMSSD (50 ± 9 ms vs. 30 ± 8 ms, p < 0.001).Conclusion: Short-duration slow deep breathing significantly lowers heart rate and blood pressure in healthy young adults, promoting parasympathetic activation and enhancing cardiovascular function. This non-pharmacological technique is an effective and accessible tool for managing stress and improving autonomic regulation.