The aim of this paper is to provide an explicit basis of the miniversal deformation of a monomial curve defined by a free semigroup -- these curves make up a notable family of complete intersection monomial curves. First, we dispense a general decomposition result of a basis of the miniversal deformation of any complete intersection monomial curve. As a consequence, we explicitly calculate this basis in the particular case of a monomial curve defined from a free semigroup. This explicit computation yields some estimates for the dimension of the moduli space of these family of curves.