In this paper we report the composition dependence of dielectric properties in Se 100−x Sn x (x=0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constant (ɛ′) and the dielectric loss (ɛ″) in the above glassy systems, in the frequency range (1kHz to 5MHz) and temperature range (300–350K) have been measured. It has been found that ɛ′ and ɛ″ both are frequency and temperature dependent and are also found to increase with increasing concentration of Sn in pure amorphous Se. The role of Sn, as an impurity in the pure a-Se glassy alloy, has also been discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have also been correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.