Mahavallathy (MV) legiyam, a Siddha herbal formulation has the indication for 21 types of megam (Sexually transmitted disorders), 18 types of kuttam (skin disorders), Puttru (cancer), Powthiram (fistula), Sori (itchy skin lesion) and Sirangu (scabies). It is widely used for cancer by many Siddha practitioners. It is prepared from 30 medicinal plants and major ingredient of legiyam is Serangottai (Semecarpus anacardium) which possess the anti-cancer activity. Standardization is required to achieve batch-to-batch consistency as well as large-scale drug manufacturing. This study aims to develop preliminary physicochemical profile of Mahavallathy legiyam. The test drug was subjected to Physico-chemical analysis, Phytochemical Analysis, Biochemical analysis, Instrumental analysis such as heavy metal analysis, HPTLC Analysis, Aflatoxin, Pesticide residue, Specific pathogen and Microbial contamination. This study showed the presence of mercury, arsenic, iron, calcium, aluminium, sulphate and carbonate through bio chemical analysis. MV legiyam contains 0.7ppm mercury in inductively coupled plasma optical emission spectrometry (ICP-OES). This study revealed the data regarding the physicochemical characterisation of MV legiyam, which will be helpful in standardising the drugs and further comparison studies.