Cosmeceuticals, combining cosmetic and therapeutic benefits, are a rapidly expanding segment in the personal care industry, driven by growing consumer demand for skincare that enhances both appearance and well-being. This chapter explores the potential and challenges of fungal-based cosmeceuticals as fungal-derived ingredients, such as polysaccharides, beta-glucans, and antioxidants, are gaining popularity in addressing skin concerns like aging, inflammation, and hydration due to their resilience, stability, and effectiveness. The importance of stability in cosmeceutical formulations, with physical, chemical, and microbiological factors affecting product integrity, is addressed. Key techniques for stability assessment, including accelerated and real-time testing, are discussed, along with case studies on fungal ingredients like Cordyceps sinensis and Ganoderma lucidum. Challenges in formulating stable fungal-based cosmeceuticals, such as microbial contamination and chemical degradation, as well as strategies for improving stability, are also discussed. The chapter concludes by emphasizing the potential of fungal-based cosmeceuticals in meeting consumer demand for natural, effective skincare solutions while underscoring the need for continued research to ensure product safety and sustainability.