<p>In this study, I re-examine the question of whether a hypothetical planet, Vulcan, could explain the anomalous advance of Mercury’s perihelion. I propose that Vulcan might be considered a type of primordial black hole with a planetary mass. The detection of this type of celestial body has become possible through modern experimental techniques, including the Optical Gravitational Lensing Experiment. Recently, an excess of ultra-short microlensing events with crossing times of 0.1–0.3 days has been reported, suggesting the possible existence of sub-Earth-mass primordial black holes in our solar system. The primordial black hole Vulcan planetary mass hypothesis could then explain the anomalous advance of Mercury’s perihelion under the influence of its gravitational attraction, remaining hidden from astronomers’ telescopes. But in this case, it will also influence the perihelion advance of the other planets. To this end, I first calculate the mutual partial contributions to the perihelion motion of all the planets by two different methods without Vulcan in a model of the simplified solar system consisting of the Sun and eight planets. Next, I include Vulcan in this model within the framework of the Newtonian theory of classical gravitation and analyze Vulcan’s influence on the perihelion advance of the inner planets, using Vulcan parameters from my previous work. These results are compared with the perihelion advances of the inner planets predicted by the theory of general relativity and with the data obtained by modern observations.</p>