  In this article, we deal with the fine boundary regularity, a weighted
H\"{o}lder regularity of weak solutions to the problem involving the fractional
$(p,q)$-Laplacian denoted by \begin{eqnarray*}
  \begin{array}{rll}
  (-\Delta)_{p}^{s} u + (-\Delta)_{q}^{s} u &= f(x) &\text{ in } \Omega
  u&=0 &\text{ in } \mathbb{R}^N\setminus\Omega;
  \end{array} \end{eqnarray*} where $\Omega$ is a $C^{1,1}$ bounded domain and
$2 \leq p \leq q <\infty.$ For $0<s<1$ and for non-negative data $f\in
L^{\infty}(\Omega),$ we employ the nonlocal analogue of the boundary Harnack
method to establish that $u/{d_{\Omega}^{s}} \in C^{\alpha}(\Bar{\Omega})$ for
some $\alpha \in (0,1),$ where $d_\Omega(x)$ is the distance of $x$ from the
boundary. A novel barrier construction allows us to analyse the regularity
theory even in the absence of the scaling or the homogeneity properties of the
operator. Additionally, we extend our idea to sign changing bounded $f$ as well
and prove a fine boundary regularity for fractional $(p,q)$ Laplacian for some
range of $s.$
