Liquefied natural gas (LNG) plants emit enormous amount of emission such as nitrogen dioxide (NO2), carbon monoxide (CO), and particulate matters (PM10). The Oman LNG LLC is the main provider of LNG and it is the largest contributor to Oman’s national economy. In November 2005, the Oman LNG commissioned a third train with a capacity of 3.3 mtpa of LNG. Only few studies have investigated atmospheric levels of pollutants released from the Oman LNG after the third train became operational. The aim of this paper, therefore, was to study the effect of ground-level concentrations of NO2, CO, and PM10 expelled from the Oman LNG’s operations on ambient air quality in the winter and summer seasons using the CALPUFF dispersion modelling system. The results indicated that the ground-level concentrations of NO2 for 1-h period in the winter and summer seasons at 2027.4 μg/m3 and 625.54 μg/m3, respectively, were significantly higher than the United States Environmental Protection Agency (US EPA) concentration limits at 188.2 μg/m3. However, the average concentrations of CO and PM10 for a 1-h exposure period were within the US EPA’s permissible standards. The results of this paper show that the Oman LNG plant’s operations are not in agreement with US EPA regulations, and major actions must be taken by the facility and the government to prevent environmental impacts on Oman’s air quality.