We demonstrated the systematic investigation of the graphene addition on the microstructural behaviour and concurrent thermoelectric properties of water-atomized p-type BiSbTe (BST)-based alloy using mechanical ball milling, and followed through the spark plasma sintering to fabricate a bulk compact specimen. X-ray diffraction results confirm the single phase of BST. The fracture surface of both specimen exhibits the homogenous distribution of grains with  irregular  shapes  in  a  random  alignment.  The  graphene  in  the  BST  provides  an  extra carrier transport leading to an increment in the carrier concentration (n) resulting in higher electrical  conductivity  (σ)  for  the  BST + Graphene  composite.  The  interface  between  two-dimensional  (2D)  graphene  and  bulk  BST  provides  a  larger  degree  of  phonon  scattering leading  to  a  maximum  reduced  thermal  conductivity  (к)  of  0.8 W  m−1K−1 compared  to pristine- BST (0.9 W m−1K−1) results in a maximum figure of merit (ZT) 1.1 at 400 K.