Pneumonia is an inflammatory condition of the lung caused by infections, which may be triggered and exacerbated by particulate matter (PM) exposure. We aimed to estimate the effect of PM on emergency department (ED) visits in pneumonia patients with septicemia after controlling for gaseous pollutants. Data on PM2.5, PM10, and other air pollutant measurements in each of the 11 air monitoring stations in Kaohsiung City of Taiwan were collected between 2007 and 2013. The medical records of non-trauma patients who were over the age of 17 years and had visited the ED with a principal diagnosis of pneumonia were extracted. Poisson models were used to examine the relationship between air pollutants and daily ED visits in pneumonia with septicemia. Interquartile increments in the levels of PM2.5, PM10, and NO2 at lag 0 were associated with increments of 25.5%, 21.61%, and 21.97%, respectively, in the number of ED visits among pneumonia with septicemia during the warm season. The effect estimates of PM2.5 were robust after adjustment for PM10 and NO2 in the two-pollutant model. PM2.5 had stronger associations with ED visits in the case of pneumonia with septicemia in relatively healthy patients, such as those without comorbid hypertension, diabetes, stroke, liver cirrhosis, respiratory disease, and malignancy. In conclusion, although the existing evidence supporting a causal relationship between PM2.5 and pulmonary dysfunctions, we proposed that PM2.5, PM10, and NO2 may play an important role in emergency visits for pneumonia with septicemia events during the warm season in southern Taiwan. The effects of PM2.5 were robust after adjustment for PM10 and NO2, especially among relatively healthy residents.