A method is described for the assembly of a magnetic core for a transformer, with the following steps: Cutting sheet metal blanks from transformer sheet, stacking the sheet metal blanks to form magnetic core segments, placing a permanent magnet at one of the magnetic core segments so that the latter is magnetized by the permanent magnet, formation of the magnetic core by placing the remaining magnetic core segments against the permanent magnet, or against a magnetic core segment already magnetized by the permanent magnet. A magnetic core is also disclosed.