Recently, the HESS collaboration has reported the detection of gamma-ray emission above a few hundred GeV from eight new sources located close to the Galactic plane. The source HESS J1813-178 has sparked particular interest, as subsequent radio observations imply an association with supernova remnant G12.82-0.02. Triggered by the detection in very high energy gamma-rays, a positionally coincident source has also been found in INTEGRAL and ASCA data. In this Letter we present MAGIC observations of HESS J1813-178, resulting in the detection of a differential gamma-ray flux consistent with a hard-slope power law, described as dN(gamma)/(dA dt dE) = (3.3 +/- 0.5) x 10(-12)(E/TeV)(-2.1 +/- 0.2) cm(-2) s(-1) TeV-1. We briefly discuss the observational technique used and the procedure implemented for the data analysis, and we put this detection in the perspective of multifrequency observations.