Synopsis K-shell fluorescence yield, width, and K β /Kα intensity ratio for Fe are calculated using the Dirac-Fock approach. Results are compared with available data. The knowledge of accurate values of atomic decay rates and fluorescence yields is fundamental in quantitative analysis in X-ray spectroscopy, plasma physics, nuclear physics, dosimetry, radiation protection, among many other areas [1]. Despite the increasing number of theoretical and experimental work concerning the determination of fluorescence yields for several elements, the available data are still scarce. Iron is one of the most abundant elements in the universe and is of extreme importance in the analysis of stellar objects like stars and galaxies. Iron spectral lines are used in plasma diagnostics and help us to know physical properties such as temperature and electron density as well as for abundance studies [2]. In this work, we present a relativistic calculation of the K-shell width, fluorescence yield and K β /K α intensity ratio in Fe using the multi-configuration Dirac-Fock (MCDF) code of De-sclaux and Indelicato [3, 4]. The code was used in a single-configuration approach, with Breit interaction and the vacuum polarization terms included in the self-consistent field calculations, and other QED effects included as perturbations. Table 1. K-shell fluorescence yield (ω K), width (eV), and K β /K α intensity ratio for iron