The study observes the effect of slow abdominal breathing on blood pressure (BP) and relate these changes to Heart Rate Variability (HRV) in prehypertensives.22 self– controlled prehypertensive volunteers were subjected to intervention of slow abdominal breathing @ of 6 breaths/min and record the ECG using standardized procedure for HRV analysis along with the systolic (SBP) and diasolic (DBP)blood pressure during their pre intervention period[@ of 20 breaths/min] ,the intervention period & post intervention period [@ of 20 breaths/min] . Recorded data in three stages were analysed using paired “t” test and Pearson test for correlation with a “p” value of <0.05 as level of significance. The study observed a marked decrease in mean SBP & DBP (P =0.001) in addition to significant decrease in mean sympathetic activity (L.F.) & increase in parasympathetic activity( H.F) (P value <0.05) during slow abdominal breathing @ 6 breaths/min from the pre intervention period @ 20 breaths /min in pre hypertensives subjects . Later on increasing the breathing rate to @ 20 breaths /min from 6 breaths/min showed a significant reversal of the values of HRV parameters, SBP and DBP in the period of post intervention. Negative though non–significant relation was observed between blood pressure reduction and change in vagal tone (HF). Slow abdominal breathing at 6 breath /min acutely decreases the SBP and DBP in prehypertensive which may be due to increase in the vagal tone[HF] with decreases in the excitability in sympathetic system[LF,LF/HF] .