In this work, the effects of luminescent coupling (LC) on the external quantum efficiency (EQE) of perovskite‐silicon tandem (PST) solar cells are quantified by means of monochromatic transient photocurrent measurements and comprehensive optoelectronic simulations that take into account both optical and electrical coupling of the subcells. It is shown that, at short wavelengths, a similar response results from both LC and silicon bottom‐cell shunts. The two contributions can be discriminated and quantified based on bias voltage and light intensity‐dependent measurements. Such measurements were conducted on state‐of‐the‐art PST cells and agree well with the behavior predicted by the simulations. For the case of polychromatic EQE simulations, a quenching of the LC effects with decreasing concentration of mobile ions is found, which is explained in terms of ion‐modulated recombination via bulk defects.