We present spherically symmetric simulations of thermonuclear explosions of a white dwarf admixed with an extended component of Fermionic dark matter, using the deflagration model with the deflagration-detonation transition. The dark matter component is comparable in size with that of the normal matter, and so the system is described by the two-fluid, one-dimensional Eulerian hydrodynamics. The dark matter is left behind after the explosion as a compact dark star in all of our considered models. Compared to explosions without dark matter admixture, the presence of dark matter lengthens the deflagration phase to produce a similar amount of iron-group elements and more thermoneutrinos. Dark matter admixed models also produce dimmer but slowly declining light curves, which are consistent with some observed peculiar supernovae. Our results also suggest a formation path for dark compact objects which mimic sub-solar-mass black holes as dark gravitational sources.