Insights into the molecular mechanism underlying nuclear envelope breakdown (NEBD) are crucial to understand dynamic changes of the nuclear envelope (NE) that occur at mitotic entry of eukaryotic cells. In this paper, we present an image processing algorithm and its implementation in KNIME, which allows to automatically quantify image data obtained from the in vitro NEBD assay. The algorithm consists of image alignment via phase correlation, nucleus identification using adaptive thresholding, morphological operations, and intensity measurements. The results of these measurements are verified using images from a known nuclear envelope disassembly assay.