Only about 20 people showed up for the rainy demonstration, including social activist Maude Barlow and several trade union leaders.
The four-metre-tall wooden horse is a snazzy reproduction of a much larger model that hid 30 Greek soldiers and ended the siege of Troy about 1184 BC.
Now straddling the sidewalk in front of Parliament's centre block, the horse warns of hidden pitfalls in the trade deal now entering its ninth and possibly final round of negotiations.
Billed as the biggest thing since 1994's NAFTA, the multibillion-dollar Comprehensive Economic and Trade Agreement will give Canadian firms preferential access to the lucrative European market.
But critics warn it has much wider implications that could erode Canada's economic sovereignty, eliminate jobs and damage companies.