The synergistic vascular protective effect of statins and angiotensin receptor blockers (ARBs) is well known, however, the pharmacokinetic interaction among these classes is yet to be understood and the necessity of developing analytical methods for their determination in vivo is gradually increased. Herein, first chromatographic separation coupled tandem mass spectrometric was developed and fully validated for simultaneous measurement of rosuvastatin (ROS) and irbesartan (IRB) in rat plasma after oral administration. The two analytes were extracted from plasma sample using acetonitrile-induced protein precipitation then separated on an Agilent Eclipse Plus ODS (4.6 × 100 mm, 3.5 μm) column by gradient elution using 6 mM ammonium formate/0.1% formic acid and ACN at a flow rate 0.4 mL min-1. Multiple reaction monitoring in positive ion mode was used for quantification of precursor to production at m/z 492.1 → 206.9 for IRB, 482.1 → 258.1 for ROS, and 409.2 → 238.2 for the internal standard, amlodipine (AML). Linearity was obeyed in the range of 1-10000 ng mL-1 and 1-5000 ng mL-1 with detection limits (S/N of 3) of 0.05 and 0.07 ng mL-1 for IRB and ROS, respectively. The current method was validated in terms of selectivity, recovery, accuracy, precision, matrix effects, and stability as per US-FDA bioanalytical guidelines. The application of our method reported her is the first to study pharmacokinetic interaction of IRB and ROS in rat plasma after a single oral dose. The area under the concentration-time curve (AUC), peak plasma concentrations (Cmax), half-life time (t1/2), and volume of distribution (Vd) of ROS and IRB were affected when the two drugs were co-administering. The current study provided a valuable tool for studying drug-drug interaction and might be useful for therapeutic drug monitoring and bioequivalence studies.