We investigate several phenomena related to FCNCs in the $$\text {3-3-1-1}$$ $\text{3-3-1-1}$ model. The sources of FCNCs at the tree-level from both the gauge and Higgs sectors are clarified. Experiments on the oscillation of mesons most stringently constrain the tree-level FCNCs. The lower bound on the new physics scale is imposed more tightly than in the previous, $$\text {M}_{\text {new}}>12 $$ ${\text{M}}_{\text{new}}>12$ TeV. Under this bound, the tree-level FCNCs make a negligible contribution to the $$\text {Br}(B_s \rightarrow \mu ^+ \mu ^-)$$ $\text{Br}(B_s\to {\mu }^{+}{\mu }^{-})$ , $$\text {Br}(B \rightarrow K^{*} \mu ^+ \mu ^-)$$ $\text{Br}(B\to K^{\ast }{\mu }^{+}{\mu }^{-})$ and $$\text {Br}(B^{+}\rightarrow K^{+}\mu ^{+}\mu ^{-})$$ $\text{Br}(B^{+}\to K^{+}{\mu }^{+}{\mu }^{-})$ . The branching ratio of radiative decay $$b \rightarrow s \gamma $$ $b\to s\gamma$ is enhanced by the ratio $$\frac{v}{u}$$ $\frac{v}{u}$ via diagrams with the charged Higgs mediation. In contrast, the charged currents of new gauge bosons significantly contribute to the decay process $$\mu \rightarrow e \gamma $$ $\mu \to e\gamma$ .