Speleothems are useful for paleoclimate reconstructions; however, environmental monitoring of the cave atmosphere is crucial to achieve an accurate interpretation of geochemical records obtained from stalagmites. This study focuses on the environmental monitoring of Larga Cave (Sierra de los Filabres, Almería), whose speleothems are being investigated for paleoclimate reconstructions. Both the external environment (rainfall, temperature) and the inner cave atmosphere (temperature, relative humidity, CO2, CH4, and 222Rn contents) have been monitored over one year. The cave atmosphere remained well ventilated during the monitoring period, as revealed by relatively low levels of 222Rn (~160 Bq/m3) and CO2 (~490 ppm). However, we identified intervals during which ventilation decreased, as evidenced by increased levels of 222Rn and higher relative humidity. During these periods, fractures in the cave ceiling became partially saturated, causing its accumulation of 222Rn inside the cavity.