Introduction: Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum. In Ayurveda, use of Mercury in Rasa-Aushadhis has been known to all of us since the era of Nagarjuna who experimented with mercury with intention to eliminate poverty from world. With proper use of mercury in medicinal formulations diseases can be cured but their improper use can lead to various diseases such as Nasabhanga, Mukhroga, Pakshaghat, Twacha Vaivarnya, Unmad and other psychic disorders and can lead to Toxicity. Mercury is an Irritant Inorganic Metal Poison. Metallic mercury is not poisonous when taken by mouth. Poisoning occurs if the finely divided particles or vaporized mercury is swallowed, inhaled or rubbed on the skin. Material & Methods: Various Samhita Granthas, Articles, Textbooks related to Mercury Toxicity were studied. Results & Conclusion: Wide use of Mercury in Ayurvedic & Siddha medicines is evident since many years. As mercury gets deposited in tissues, it can lead to toxicity as a chronic effect. Also, occupational exposure by means of inhalation of vapors can cause many symptoms such as conjunctivitis, stomatitis, cough, dyspnoea, etc. Case studies also reported how Mercury toxicity can affect CVS, Respiratory & CNS systems. PM Appearances, Medicolegal aspect, Treatment, of Mercury Toxicity and Ayurvedic description were discussed.