In order to find a fully natural substitute of pentaerythritol (PER), which is the basic carbon source in thermal swelling systems, a powder of cocoa shells (CS) was tested in intumescent coatings based on poly(vinyl acetate) (ICs). Generally, CS are the main waste by-products of cocoa production, and their utilization is limited. The coating materials were mainly compounded using melamine (a blowing agent), ammonium polyphosphate (a dehydrating agent), and the same doses of PER, CS or their mixtures (PER/CS). They were primarily investigated using a gas flame-heated furnace (according to a cellulosic fire curve), TGA, and DSC techniques. The CS addition markedly affected charring processes of ICs during the fire test and improved intumescence effectiveness and thermal insulation time parameters (from 15.9 to 23.6 a.u. and from 28.2 to 30.9 min, respectively). Moreover, the natural additive increased compression strength of charred ICs on a steel substrate (from 1.48 to 1.88 kPa). The best performance properties were noted for IC with the PER/CS mixture containing 10 wt% of the organic component – in this case all the tested features were improved.