The most recent attack was midday Monday, when an 18-year-old woman walking on a path was approached from behind, The Ottawa Citizen reported.
The attacker was unsuccessful, as the woman whirled around and threw coffee in his face, police said.
As with the eight other attacks, the 5-foot-6 white man with a goatee in his early 20s casually walked away, the report said.
The attacks began April 14 and have targeted women walking alone. In some of the incidents, the women were sexually groped. In one case, the victim was knocked to the ground, police said.
There were three separate attacks on April 16, the report said.