The objective of the present work was to develop a sensitive, selective, accurate and precise stability-indicating HPLC method for quantification of degradation products and process-related impurities in fesoterodine fumarate extended-release tablets. The degradation profile was studied by conducting forced degradation studies and all the degradation products formed during degradation were separated. A chromatographic separation was achieved by using Waters Symmetry C18, 250 × 4.6 mm, 5 μm column, maintained at 30◦C. Mobile phase A (0.05% trifluoroacetic acid in water) and mobile phase B (90% of 0.02% TFA in methanol and 10% of water) were used in gradient elution mode. A total of 75 μL of each solution was injected and peak responses were quantified at 220 nm. The method was found specific, precise, accurate, linear, rugged, robust and sensitive. During stability studies of fesoterodine fumarate extended-release tablets, one unknown impurity at relative retention time 1.37 was found increasing beyond the identification threshold. This impurity was isolated by using Preparative HPLC and structure was elucidated using mass and NMR spectroscopy. This method is a simple, inexpensive HPLC method that can be used as a routine quality control test for the estimation of impurities in fesoterodine fumarate extended-release tablets. © The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com