Introduction: A new specific, accurate and selective liquid chromatography/tandem mass spectrometry (LC-MS/MS) technique was desirable for the assessment of erdafitinib in human plasma. Aim: To develop an LC__ampersandsignndash;ESI-MS/MS method for the quantification of anticancer agent erdafitinib in human plasma and its validation as per the USFDA guidelines. Methodology: Propranolol (internal standard) reference drug utilized for the quantification of erdafitinib. Extraction of 250__ampersandsignmu;L plasma with liquid extraction technique, analyte components were eluted on symmetry (50 __ampersandsigntimes; 4.6mm; 5__ampersandsignmu;m) C18 analytical column. Mass detection system was executed by utilizing MRM (multiple reaction monitoring) with +ve ionization mode and electrospray ionization. Developed procedure was subjected for validation according to FDA guidelines in concentration levels between 69.95__ampersandsignndash;2798.00ng/mL for erdafitinib with r2 value of 0.9992. Results: The intraday and interday precision were within 4.11% and the assay accuracy was 97.95__ampersandsignndash;104.91 % of the nominal values. Matrix factor ranges from 95.61__ampersandsignndash; 103.84 % with a %CV of 3.63 for analyte at HQC and MQC levels, matrix factor range was 94.32__ampersandsignndash;104.01% with a %CV of 3.89. Conclusion: The developed process can be successfully applied for routine analysis in quality control, pharmacokinetic and forensic studies of biological samples.