We present a comprehensive investigation of the magnetic properties of stage-1 graphite intercalated FeCl3 using a combination of DC and AC magnetic susceptibility, thermoremanent magnetization, and field-dependent magnetization measurements. This van der Waals system, with a centrosymmetric honeycomb lattice, combines frustration and disorder, due to intercalation, and may be hosting topologically nontrivial magnetic phases. Our study identifies two magnetic phase transitions at Tf1≈4.2 K and at Tf2≈2.7 K. We find that the paramagnetic state, for T>Tf1, is dominated by short-range ferromagnetic correlations. These build up well above Tf1 and lead to a significant change in magnetic entropy, which reaches ΔSPkM=−5.52 J kg−1K−1 at 7 T. Between Tf1 and Tf2, we observe slow spin dynamics characteristic of a cluster glasslike state, whereas for T<Tf2, our results indicate the onset of a low-temperature long-range ordered state. The analysis of the experimental results leads to a complex phase diagram, which may serve as a reference for future investigations searching for topological nontrivial phases in this system.