Of the 500 people Canada is sending to monitor the vote, 338 will be with the independent election observation mission led by Harris and Andreychuk, Prime Minister Stephen Harper said in a statement Tuesday.
"Canada has been steadfast in its support for Ukraine and we are proud to once again play a role in fostering democracy and good governance at this challenging time in that country," Harper said.
The remaining 162 will participate in observation missions run by the Organization for Security and Co-operation in Europe.
Andreychuk is a Saskatchewan Conservative appointed to the upper house by Brian Mulroney in 1993. A key figure in the Canadian-Ukrainian community, Andreychuk led similar Canadian delegations in 2010 and 2012.
Harris was Progressive Conservative premier of Ontario from 1995 to 2002, winning two majority governments. Harper said Harris will bring insights and expertise from the democratic process and executive leadership.
The first round of Ukraine's presidential election will be held on May 25, 2014. If needed, a second round of voting will be held in June.
The Harper government has been a vigorous supporter of Ukraine in the face of Russia's annexation of the Crimean Peninsula and efforts to destabilize other regions of the country.
Harper — who visited Ukraine in March, as the crisis was building —has blunt in criticizing Russian President Vladimir Putin's actions against Ukraine. Both he and Foreign Affairs Minister John Baird have portrayed him as a threat to world peace.
Harper's government has imposed travel and economic sanctions against a number of Russian and Ukrainian individuals and institutions.
Baird made a quick tour of eastern European capitals to pledge support and urge solidarity against Russian sabre-rattling in the region.
Canada has made numerous contributions to recent NATO efforts in Europe. It sent a frigate to join NATO's standing task force in the eastern Mediterranean, six CF-18 jet fighters to operate out of Romania, and troops from 3rd Battalion, Princess Patricia's Canadian Light Infantry to participate in a land exercise in Poland.
Also on HuffPost