The ceremony is set for Saturday, and if Harper does indeed attend it will mark his second trip to Ukraine since mass protests toppled the government of former president Viktor Yanukovych in February.
Russia has since annexed Crimea and Ukrainian forces have battled pro-Russian forces in the country’s east. In response, Canada has levied sanctions against Russia.
“Canada has been a leader in the global response to Russian aggression in Ukraine,” said a statement about the trip released by the Prime Minister's Office.
Canada also sent a large team of election officials to help oversee Ukraine’s national election, which Poroshenko — a billionaire chocolate magnate — won in May.
Harper’s decision to stand behind Poroshenko during the swearing-in – several other high profile politicians including U.S. Vice-President Joe Biden will be there as well – is likely intended to send a message to Russian President Vladimir Putin.
Harper has taken a harder line than most toward the Russian leader, the CBC’s Chris Hall reports.
“His boldness has increased since Russian troops first made an open grab for power in Crimea,” Harper said in a recent speech.
"The impact of the Putin regime's expansionism and militarism extends beyond Ukraine. It threatens the security of our Eastern European allies and, by extension, the stability and security of the world.”
Hall said Canadian officials may even push for additional sanctions against Russia.
Prior to the Ukraine trip, Harper will be in Poland, Belgium and France.
Canadian officials said Harper is not set to meet with Putin during his trip.