Naypyidaw to meet Myanmar's President Thein Sein, according to a statement from the US embassy in Yangon.
Mitchell was nominated to the role by President Barack Obama, who has pursued a policy of greater engagement with Myanmar as the Southeast Asian nation emerges from decades of junta rule, which ended last year.
The US has eased some of its strict sanctions against the country as a reward for a series of reforms including holding landmark by-elections that saw Aung San Suu Kyi and other members of her party elected to parliament.
Mitchell arrives in Naypyidaw days after Suu Kyi -- whose democracy struggle saw her locked up for 15 of the last 23 years by the generals -- made her debut in parliament, lending legitimacy to a legislature that remains dominated by the army and its political allies.
Washington withdrew its ambassador to Myanmar after a crackdown on a democracy uprising in 1988 and elections won by Suu Kyi's democracy party two years later that were never recognised by the junta.
But a recent slew of positive changes from Thein Sein's quasi-civilian government, which took power last year, have surprised the West and driven hopes of a democratic future for the country.
Key US demands have been answered to a certain extent by the reforms, which have included releasing hundreds of political prisoners, seeking ceasefires with major ethnic rebels and ushering Suu Kyi's party into mainstream politics.
"As an iron fist has unclenched in Burma, we have extended our hand, and are entering a new phase in our engagement on behalf of a more democratic and prosperous future for the Burmese people," Obama said in May when he named his new ambassador and announced an easing of investment sanctions.
US law currently requires the president to restrict imports from Myanmar and bans US investment and export of financial services to the country.
But American businesses are pushing for a further relaxation of punitive measures against the impoverished but resource-rich country, which is seen as a major potential growth market for international investors.
Myanmar's parliament is currently considering a new investment law and a series of other measures aimed at liberalising the economy, which was left in tatters by decades of mismanagement, cronyism and isolation under the junta.
At Mitchell's confirmation hearing in June, senators pressed the Obama administration to allow investment by US energy companies, voicing fear that they could lose out to foreign competitors.
Human rights groups have voiced concerns that the oil and gas industry has fuelled abuses like forced labour in the country.
Mitchell said last month that reform in Myanmar "is not irreversible" and raised the continuing detention of "hundreds of political prisoners" as a key concern.
Last week democracy activists said at least 20 political prisoners were released as part of an amnesty, but several hundred are thought to remain incarcerated.