A Stability-Indicating reversed-phase high performance liquid chromatography (RP-HPLC) Method was developed for the Simultaneous Determination of Formoterol Fumarate (FOR), Tiotropium Bromide (TRI), and Ciclesonide (CLS) in a Pulmonary Drug Product. The desired chromatographic separation was achieved on the Zorbax SB C8, 5 μm (150 × 4.6 mm) column, using gradient elution at 230 nm detector wavelength. The optimized mobile phase consisted of a 0.2 % v/v perchloric acid as solvent-A and acetonitrile as solvent-B. The developed Method separated FOR, TRI, and CLS in the presence of its five unknown degradation Products within 10 minutes. The Stability-Indicating capability was established by forced degradation experiments and the separation of unknown degradation Products. The developed RP-HPLC Method was validated according to the International Conference on Harmonization (ICH) guidelines. This validated Method was applied for the Simultaneous estimation of FOR, TRI, and CLS in commercially available Triohale(®) pMDI (Pressurized Metered-Dose Inhaler) samples. Furthermore, this Method can be extended for individual estimation of FOR, TRI, and CLS in various commercially available Pulmonary dosage forms.