We present co‐crystallization as an approach to tuning spin crossover (SCO) properties of mononuclear Mn(III) Schiff‐base complexes. Complexes [Mn(5‐F‐sal‐N‐1,5,8,12)]ClO4·0.5carbazole (cocrystal 1a) and [Mn(5‐F‐sal‐N‐1,5,8,12)]PF6·0.5carbazole (cocrystal 2b) are synthesized by the co‐crystallization of their parent complexes ([Mn(5‐F‐sal‐N‐1,5,8,12)]Y, Y = ClO4− (1); Y= PF6− (2)) with the carbazole and they both exhibit HS electronic configurations between 2 and 300 K. While, the parent complex 1 shows a nearly complete SCO with T1/2 = 100 K and complex 2 maintains a high‐spin (HS) state. The introduction of carbazole as the third component has a great influence on cation‐anion crystal packing and finally the cooperative effects of the SCO complexes.