Polyherbal formulations, consisting of multiple plant extracts or herbal ingredients, have become increasingly popular in traditional and alternative medicine practices. However, ensuring their chemical stability is essential for maintaining therapeutic efficacy and safety. This chapter provides a systematic and comprehensive examination of the factors influencing the chemical stability of polyherbal formulations. It covers various aspects including degradation pathways, storage conditions, and formulation strategies that impact stability. Understanding the degradation pathways is crucial as it allows for the identification of potential chemical reactions that may occur within the formulation. Factors such as temperature, humidity, light exposure, and oxygen can significantly influence the stability of polyherbal formulations during storage. Additionally, the selection of excipients and formulation techniques play a vital role in maintaining stability. Analytical techniques such as chromatography and spectroscopy are widely employed for assessing the stability of polyherbal formulations. High-performance liquid chromatography (HPLC), gas chromatography (GC), and mass spectrometry (MS) are commonly used methods for analyzing the chemical composition and degradation products of these formulations. Spectroscopic techniques like UV-Vi spectroscopy and infrared (IR) spectroscopy are also valuable tools for monitoring chemical changes. By understanding the chemical stability of polyherbal formulations, manufacturers can ensure product quality and consistency. Furthermore, regulatory authorities can establish guidelines for stability testing and shelf-life determination of these formulations. This comprehensive overview aims to provide valuable insights for researchers, manufacturers, and regulatory agencies involved in the development, production, and regulation of polyherbal products. It emphasizes the importance of systematic studies on chemical stability to enhance the efficacy and safety of polyherbal formulations in healthcare practices.