<p>The main aim of this research is to study the sufficient conditions for the existence of the mild solution and approximate controllability of a class of Caputo conformable fractional neutral-type stochastic system with the instantaneous impulsive effects and nonlocal conditions in a separable Hilbert space. Since, the conformable fractional derivative retains several classical properties such as the mean value theorem, Rolle’s theorem, the product and quotient rules, and linearity, which distinguish it from traditional fractional derivatives, including the Riemann-Liouville, Caputo, and Hilfer derivatives. Therefore, the conformable derivative is simpler and faster but ignores history, while the Caputo conformable derivative offers a balance capturing some memory with easier calculations. Firstly, the Riemann-Liouville conformable fractional integral operator is used to convert the proposed stochastic control system into an equivalent fixed point problem. Then, the fixed point approach is employed to derive the results. The main tools applied in this study are fractional calculus, semigroups of bounded linear operators, stochastic analysis, and Krasnoselskii’s fixed point theorem. Further, the approximate controllability results of the proposed stochastic control system are established under the consideration that the corresponding linear system is approximate controllable. At the end, we provide an example to illustrate our theoretical findings.</p>