We present the results of an analysis of data collected by IceCube/DeepCore in 2010-2011 resulting in the first significant detection of neutrino oscillations in a high-energy neutrino telescope. A low-energy muon neutrino sample (20-100 GeV) containing the oscillation signal was extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV -10 TeV) was extracted from IceCube data in order to constrain the systematic uncertainties. The non-oscillation hypothesis was rejected with more than 5σ. We fitted the oscillation parameters Δm232 and sin22θ23 to these data samples. In a 2-flavor formalism we find Δm232=(2.5±0.6)⋅10−3 eV2 and sin22θ23>0.92 while maximum mixing is favored. These results are in good agreement with the world average values.