Cooperative spin crossover (SCO) materials exhibit first‐order phase transitions in the solid state, between the high‐spin (HS) and low‐spin (LS) states. Elastic long‐range interactions are the basic mechanism for this particular behavior and are described well by the Ising‐like model, which allows the reproduction of most of the experimental results in the literature. Until now, this model has been applied with an interaction parameter between the molecules, which is considered to be independent of the states. In this contribution, we extend the Ising‐like model to include interaction energy that depends on the spin states and apply it to study SCO nanoparticles. Our research shows that following this new hypothesis, the equilibrium temperature shifts toward higher values.