The aim of this paper is to investigate the effects of petroleum fuel excise tax costs on productivity of generator-reliant firms in Uganda. Most studies investigated the association between corporate tax and firm productivity, value added tax and firm productivity. This study contributes to the neglected area on the influence of petroleum excise tax costs on firm productivity. In this paper, we employ the ordinary least square (OLS) method for estimations. The results show a negative impact of petroleum fuel excise tax costs on the productivity of manufacturing firms, driven by the severe tax burden. In addition there is a negative significant association between tax cost and household welfare. Therefore tax policy actors should formulate policies that not only raise tax revenue but also boost business growth.