Cyclohexane and methylcyclopentane isomerization were carried out under mild conditions using an ionic liquid consisting of n-butylpyridinium chloride and aluminum chloride as catalyst. The ionic liquid showed reasonably high catalytic activity in both reactions with a selectivity to corresponding products of 100%. In the case of cyclohexane isomerization, the thermodynamic equilibrium methylcyclopentane reversible arrow cyclohexane was almost achieved. For the reaction of cyclohexane isomerization, a kinetic study was performed, and the rate constants and the activation energy of the process were determined.