Abstract We propose a new physics model which has a cold dark matter candidate and can explain the b → sμ + μ − anomaly at the same time. Our model includes a scalar quark q ˜ $$ \tilde{q} $$ and a scalar lepton ℓ ˜ $$ \tilde{\ell} $$ which are SU(2) L -doublet as well as a Dirac fermion N which is SU(2) L -singlet. The new particles are charged under a gauged U(1) X group which is spontaneously broken to a discrete Z 2 symmetry by a dark scalar S. The remnant Z 2 symmetry stabilizes the dark matter. Box diagrams with q ˜ $$ \tilde{q} $$ , ℓ ˜ $$ \tilde{\ell} $$ , and N running inside the loop can generate the correct Wilson coefficients C 9 μ  = − C 10 μ to accommodate the b → sμ + μ − anomaly while avoiding constraints such as B s − B ¯ s $$ {B}_s-{\overline{B}}_s $$ mixing. The dark matter annihilation into a second generation lepton pair via t-channel ℓ ˜ $$ \tilde{\ell} $$ -exchanging process plays an important role in producing the current dark matter relic abundance of the universe, showing a strong interplay between the flavor and dark matter physics. We also discuss dark-gauge-interaction-dominated and Higgs-portal-dominated scenarios for dark matter physics.