His mother was a granddaughter of the fourth daimyō of Yonezawa Domain, Uesugi Tsunanori.His childhood names were "Matsusaburō" (松三郎) and "Naomatsu" (直松).

After arriving in Yonezawa, from 1763 he became an ardent disciple of the Neo-Confucian scholar Hosoi Heishu, whose teaching would strongly influence his political philosophy and governing outlook.

Harunori began by imposing stringent fiscal restraints on spending, setting an example by wearing cotton clothes instead of silk and having his meals consist of one bowl of soup and one vegetable.

As soon as these efforts started to show results, the domain was then hit with a demand from the Shogunate to rebuild the western bailey of Edo Castle.

[3] Education was necessary to create the brilliant men required to enrich the country, and he reopened the han school which had closed down due to financial constraints and invited scholars from Edo to teach.

Another policy change ensured adequate water from the mountains for the rice fields by enlisting retainers and samurai to dig irrigation ditches and to repair dikes.

He revealed his views on governance and the role of a feudal lord in a letter to his son Haruhiro: The state (国家, kokka) is inherited from one's ancestors and passed on to one's descendants; it should not be administered selfishly.