This article studies the approximate controllability for a class of fractional control system with semigroup operators governed by differential equations with Hilfer fractional derivatives of order α ∈ ( 0 , 1 ) and type β ∈ [ 0 , 1 ] in Hilbert spaces. First, we establish a set of sufficient conditions for the approximate controllability for Hilfer fractional stochastic differential equation with non-dense domain in Hilbert spaces. The existence results are obtained by using the fractional calculus, semi-group theory, Wiener process and fixed point technique to prove our main results. Further, we extend the result to study the approximate controllability concept. An example is provided to illustrate the application of the obtained theory.