In this work, an accurate, sensitive, reproducible and precise stability indicating high performance liquid chromatographic (HPLC) method and ultra violet (UV)-visible spectroscopic method were established for the quantification and validation of β adrenergic drug mirabegron in bulk and its pharmaceutical dosage form. High performance liquid chromatography is a physical separation technique for a mixture of compounds that are dissolved in solution. Mirabegron is in a class of medications called diuretic. The HPLC method was developed with proposed chromatographic condition with mobile phase containing acetonitrile: water (50:50, v/v) adjusted pH 9 with 1 mL of 1% TEA. Accomplishment of UV-visible spectroscopic determination was done at wavelength maxima of 247 nm using methanol as a solvent. The linearities were in the range of 2-18 µg/mL for UV-visible spectroscopic method and 0.01-20 µg/mL for HPLC method, respectively. Validation of proposed method has been accomplished with respect to linearity, accuracy, precision, specificity and robustness. Forced degradation study has been performed under different conditions like acid and alkali hydrolysis, chemical oxidation, dry heat degradation and photolytic degradation study by use of stock solution of mirabegron and quantification has been achieved by proposed reverse phase-liquid chromatography (RP-LC) method. Mirabegron is susceptible to acid and base hydrolysis, chemical oxidation, dry heat and photolytic degradation studies; found that degradants are well resolve from parent drug peak of mirabegron. Due to the sensitivity, promptness and accuracy of methods, we rely on that the both intended methods will be useful for the regular quality control analysis and quantification of drug in bulk and pharmaceutical dosage form.