This paper presents a field study carried out on a novel self-regulating active beam system installed in an office building located in Jönköping, Sweden. The system consists of two parts: an air handling unit (AHU) to satisfy ventilation requirements, and a water circuit to meet sensible heating and cooling loads. The novelty of the system is in relation to the water circuit, which is able to provide simultaneous heating and cooling through a single loop with water at near room air temperature. The field study evaluated both the performance of the system and the indoor climate in the building. The performance of the system was monitored for a one-year period through sensors placed along the water circuit and the AHU. The indoor climate in the building was assessed by measuring relevant physical parameters and by conducting a survey among occupants. Results show that the system is capable of maintaining indoor air temperatures between 21 and 24 °C by circulating water at temperatures of about 22 °C. The annual average indoor air temperature during working hours was 22.6 °C ± 0.6 °C, indicating low variation during the year. Answers to questionnaires revealed that occupants were satisfied in terms of thermal comfort, achieving an acceptability rate of 90%. An average thermal sensation vote of −0.38 in winter and −0.48 in summer was obtained, indicating that occupants generally felt slightly cold.