We analyze constraints on anomalous couplings of the $Wtb$ vertex. In particular, we look at scenarios when two of four possible couplings are allowed to vary from their Standard Model values and obtain corresponding indirect constraints from three channels in B-physics: $B_{d,s}-\bar{B}_{d,s}$ oscillations, inclusive decay $B\to X_s\gamma$ and inclusive decay $B\to X_s\ell^+\ell^-$. We compare our results with constraints of similar scenarios obtained from direct experimental study of the $Wtb$ vertex in the t-channel single top quark production cross section. We conclude that in most two-dimensional scenarios indirect constraints are more rigid. So far, no deviations from the Standard Model have been found.