To provide a water-based ink composition for a ballpoint pen, capable of securing the good ink-ejectability over a long-distance writing by suppressing the wear of a ball-receiving seat caused by the rotation of a ball, and enabling long-term writing without damaging the initial writing feeling, and to provide the ballpoint pen including the ink composition.

The water-based ink composition for the ballpoint pen contains at least a coloring matter, water, and a diester derivative of dicarboxymethylsuccinic acid and/or a salt thereof. The ballpoint pen includes the water-based ink composition for the ballpoint pen.