McCain and other senators will meet president Raimonds Vejonis at Riga Castle as part of a three-day visit taking in all three Baltic states.
McCain is a noted hawk on Russia's aggessive policies in Ukraine and his visit is likely to offer reassurances that many members of the Republican party view the security of the Baltic states as important.
He is also urging a much more coordinated and robust approach to cybersecurity in the wake of Russian hacking efforts.
McCain has visited the Baltic states several times previously, including at the opening of the NATO Strategic Communications Center of Excellence in Riga in 2014.
Meanwhile US President-elect Donald Trump, also of the Republican party, and Russian President Vladimir Putin have continued their expressions of mutual admiration.
Vladimir Putin said today about Hillary and Dems: "In my opinion, it is humiliating. One must be able to lose with dignity." So true!— Donald J. Trump (@realDonaldTrump) December 24, 2016
Just in: Trump releases letter to him from Putin pic.twitter.com/oa1haK5wSV— Jim Acosta (@Acosta) December 23, 2016