A water sprayer with a water spraying adjustment mechanism including a body and a rotatable cap is disclosed. The body includes an outer tubular wall with a threaded outer surface forming a central axial bore extrusion defining an inner chamber, an inner tubular wall within the inner chamber coaxially distributed with the outer tubular wall and constructed with a plurality of slotted grooves defining a plurality of grooved water runners, and an inlet portion being adapted to connect a source of pressurized water. The rotatable cap includes an inner tubular wall with an inner surface blocked around the grooved water runners, an outer tubular wall threaded on the outer tubular wall of the body for sealing the annular inner chamber, and a plurality of water outlets formed on the outer tubular wall of the rotatable cap and communicating with the grooved water runners for water spraying. When the rotatable cap is rotated, the blocking condition between its inner tubular wall and the grooved water runners is changed to achieve an adjustment of water spraying rate.