Anne, 68, began her visit by meeting the country's president Kersti Kaljulaid in the capital Tallinn to discuss security and foreign relations between the UK and Estonia.
The Queen's only daughter also laid commemorative wreaths at the Estonian War Memorial and the Commonwealth War Graves near Tallinn.
According to Royal Central the month of May was an unusually quiet period for the dedicated royal, with Anne carrying out a total of 36 engagements.
In 2019 so far, the Princess Royal has chalked up 196 events while in 2018 her total came to a staggering 518.