In this paper, we deal with an Ornstein–Uhlenbeck process driven by sub-fractional Brownian motion of the second kind with Hurst index H∈(12,1). We provide a least squares estimator (LSE) of the drift parameter based on continuous-time observations. The strong consistency and the upper bound O(1/√n) in Kolmogorov distance for central limit theorem of the LSE are obtained. We use a Malliavin–Stein approach for normal approximations.