A simple, sensitive and specific liquid chromatography?tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of Rucaparib (RP) in human plasma using Rucaparib-d3 (RPD3) as an internal standard (IS). Chromatographic separation was performed on Xbridge C18, 50 x 4.6 mm, 5 m column with an isocratic mobile phase composed of 10mM Ammonium formate and Methanol in the ratio of (20:80 v/v), at a flow-rate of 0.7 mL/min. RP and RPD3 were detected with proton adducts at m/z 323.4  170.1 and 328.4 ? 170.1 in multiple reaction monitoring (MRM) positive mode respectively. Liquid-Liquid extraction method was used to extract the drug and IS. The method was validated over a linear concentration range of 5.0-5000.0 pg/mL with correlation coefficient (r2) ≥ 0.9994. This method demonstrated intra and inter-day Precision within 0.7 to 2.0 and 0.7 to 2.7 % and Accuracy within 101.4 to 102.4 and 99.5 to 104.8 %. Rucaparib (RP) was found to be stable throughout freeze-thawing cycles, bench top and postoperative stability studies.