We report on synthetic helium beam emission spectroscopy (BES) in fusion edge plasmas, as enabled by the 3D kinetic (neutral particle) transport code EIRENE. We also review and upgrade the underlying atomic helium data base, resorting to the most recent version of the Goto–Fujimoto collisional-radiative code and a recommended and publicly exposed reference cross section data set from an internationally coordinated (IAEA) evaluation activity. On the example of the Wendelstein 7-X (W7-X) stellarator, we use both the upgraded transport code and data base to simulate the penetration of and radiation from thermal helium used for BES in the island divertor region. This allows to evaluate the applicability of the diagnostic in different plasma backgrounds, simulated with the 3D edge plasma Monte Carlo code EMC3-EIRENE, and with different levels of refinement of underlying atomic data. The sensitivity of the diagnostic to the atomic data set—which is crucial for a quantitative determination of electron density and temperature profiles—is investigated and discussed, as well as the effects of p-He beam widening and correlated line-of-sight integration.