Among the numerous thermoelectric compounds, ${\beta}$-Zn$_4$Sb$_3$ has gained significant interest as a promising thermoelectric material due to its effective working temperature range and enhanced figure of merit (ZT) values. In this work, the effect of Se doping in ${\beta}$-Zn$_4$Sb$_3$ system has been studied. The structure refinement of the prepared Zn$_{3.9}$Se$_{0.1}$Sb$_3$ solid solution was carried out using Rietveld refinement analysis, which confirms that the compound crystallizes in hexagonal rhombohedric structure with R-3c space group. Temperature-dependent electrical conductivity (${\sigma}$) of the sample has been measured in the temperature range of 300–610 K. At room temperature, the electrical conductivity value of the sample was found to be high (${\sim}$1919 S m$^{-1}$) and it tends to decrease upon increasing the temperature up to 514 K and thereafter slightly increases, which indicates the typical metallic to semiconductor transition behaviour of the prepared compound. The positive Hall coefficient (R$_H$) value reveals that the holes are the dominant charge carriers (p-type) in the prepared sample. The power factor value (${\sigma}$S$^2$) of the sample increases linearly with increase in temperature up to 610 K. Hence the Se substitution in pristine ${\beta}$-Zn$_4$Sb$_3$ possesses greater effect in inducing superior thermoelectric power factor values. Temperature-dependent total thermal conductivity ($k_{total}$) of Zn$_{3.9}$Se$_{0.1}$Sb$_3$ sample is measured in the temperature range of 300 to 610 K. At room temperature, the $k_{total}$ value of the sample was found to be very low (${\sim}$1 Wm$^{-1}$ K$^{-1}$) and it decreases linearly with increasing the temperature. At 610 K, the sample shows merely ultra-low-thermal conductivity value (${\sim}$0.6 Wm$^{-1}$ K$^{-1}$). A peak ZT value of ${\sim}$0.3 was obtained in Zn$_{3.9}$Se$_{0.1}$Sb$_3$ solid solution at 610 K, which was found to be quite competitive with the current thermoelectric materials.