The $k-$ Fibonacci numbers $F_{k,n}\:(k>0)$, defined recursively by $F_{k,0}=0$ , $F_{k,1}=1$ and $F_{k,n}=kF_{k,n}+F_{k,n-1}$ for $n\geq1$ are used to define a new class $\mathcal{S}\mathcal{L}^k$. The purpose of this paper is to apply properties of $k$-Fibonacci numbers to consider the classical problem of estimation of the Fekete–Szegö problem for the class $\mathcal{S}\mathcal{L}^{k}$. An application for inverse functions is also given.