Climate, glacier mass balance, and subsequently river discharge are investigated based on high-resolution time series (1993–2005) from the Low-Arctic Mittivakkat Glacier catchment at the Ammassalik Island (65°N), Southeast Greenland. Meteorological data from the Mittivakkat Glacier catchment (18.4 km²) together with standard synoptic meteorological data are extrapolated from 1898 to 1993 to estimate variations and trends in air temperature, glacier net mass balance, and catchment runoff. Characteristic variations in meteorological conditions within the catchment, between the coastal (Station Coast) and the glacier area (Station Nunatak) during the investigation period occur: ~15% lower annual solar radiation, four weeks longer snow-free period, and ~50% higher maximum snow depth in the coastal area. Further, decreasing mean annual air temperatures (MAAT) occur in the coastal area (-0.13.C y^-1) during the highresolution investigation period, indicating an approximately 20-day shorter thawing period, while the higher glacier area undergoes an increasing MAAT (0.09.C y^-1), an approximately 40-day longer thawing period, a 60-day longer snow-free period, and an (linear trend) increasing release of melt water from the exposed glacier surface. The Mittivakkat Glacier net mass balance has been almost continuously negative averaging -0.59±0.51 m w.eq. y^-1 during the recent continuous observations, corresponding to 0.4% y^-1 loss of volume. Further, the glacier mass balance observations indicate an increasing negative trend. The total annual runoff from the catchment for the period 1993–2004 ranges between 24.4 and 42.0.10⁶ m3 (1,326–2,282 mm w.eq. y^-1), averaging 36.3.10⁶ m³ (1,973±281 mm w.eq. y^-1). Changes in air temperature within the last 106 years (1898–2004) show an average increase of 1.3.C for the catchment: An increase highest for the in winter season of 3.1.C. The period 1995–2004 was the warmest 10 year period within the approximately last 60 years. The glacier net mass balance from 1898–2004 indicate an average glacier recession of -0.55±0.53 m w.eq. y^-1, and a cumulative estimated balance of -56.7 m w.eq.; 89 out of 105 balance years had a negative estimated net mass balance. Average annual runoff (1898–2004) was estimated to 1,957±254 mm w.eq. y^-1, with a range between 2,522 and 1,326 mm w.eq. y^-1, respectively.