We study the fractional maximal commutators M b,𝜂 and the commutators [b, M 𝜂 ] of the fractional maximal operator with b ∈ BMO(X) in the variable Lebesgue spaces L p(•) (X) over bounded quasi-metric measure spaces. We give necessary and sufficient conditions for the boundedness of the operators M b,𝜂 and [b, M 𝜂 ] on the spaces L p(•) (X) when b ∈ BMO(X). Furthermore, we obtain some new characterizations for certain subspaces of BMO(X).