A concentric raised bog is a common mire type in the southern boreal zone. The mires play an important role in the hydrological cycle of the environment, as their moisture is usually significantly different from open agricultural land or forest. The hydrological parameters, such as soil moisture (SM), are increasingly assessed by means of remote sensing. However, the microwave radiation properties of bogs have not been widely studied in the scope of L-band radiometry, an important technology for SM observations. In order to address this topic, this letter presents an analysis of measurements of a concentric open bog with a 1.4-GHz airborne radiometer. The series of airborne measurements are collected, along with ground measurements, in southern Finland. A two-layer emission model is used to simulate microwave emission of the bog in different moisture conditions. Results show that 1.4-GHz radiometry is sensitive to bog surface conditions, such as changes in moisture content and distribution. We also show that despite the significant difference in soil moisture, the bog has emissivity characteristics more similar to agricultural rather than forested area.