A solenoid valve, particularly for a hydraulic braking system of a motor vehicle, includes a valve sleeve in which a pole core is fixed and an armature is disposed in an axially displaceable manner. The armature includes at least one longitudinal groove in the outer shell surface thereof. A spring washer is configured to be braced between the armature and the pole core. The end face of the armature facing the pole core is configured to be at least substantially convex, and the end face of the pole core facing the armature is configured to be at least substantially concave. A braking system includes the solenoid valve.