A filtration faucet system includes a filter housing for mounting underneath a faucet countertop and a filter cartridge. The filter housing has a filter compartment, a water inlet adapted for operatively linking to a water source, a filtered water outlet adapted for operatively linking to a first water opening of a faucet device, and an unfiltered water outlet adapted for operatively linking to a second water opening of the faucet device. The filter cartridge is supported in the filter compartment and is adapted not only for filtering water flowing from the water inlet to the filtered water outlet before the water exits at the first water opening but also for guiding the water directly flowing from the water inlet to the unfiltered water outlet before the water exits at the second water opening.