A very long-standing problem in Algebraic Geometry is to determine the stability of exceptional vector bundles on smooth projective varieties. In this paper we address this problem and we prove that any exceptional vector bundle on a smooth complete intersection $ 3$-fold $ Y\subset\mathbb{P}^n$ of type $ (d_1,\ldots,d_{n-3})$ with $ d_1+\cdots+ d_{n-3}\leq n$ and $ n\geq 4$ is stable.