Following her husband's accession as King Frederick I, Ulrika Eleonora served as his queen consort until her death in 1741.

Her deceased older sister, Hedvig Sophia, had left a son, Charles Frederick of Holstein-Gottorp, who had the better claim by primogeniture.

Ulrika Eleonora asserted that she was the closest surviving relative of the late king (the idea of proximity of blood) and cited the precedent of Queen Christina.

During her childhood, Eleonora was somewhat overlooked in favor of this elder, more extroverted and talented sister, princess Hedvig Sophia.

Her elder siblings enjoyed riding and dancing and reportedly somewhat looked down upon her as she did not have the courage to participate in their games and was easily brought to tears.

From 1700, she took care of her dominating grandmother, Hedwig Eleonora of Holstein-Gottorp, during her brother's absence in the Great Northern War.

As their brother Charles XII was unmarried and childless, Ulrika Eleonora was regarded as a likely future heir to the throne, and was thereby attractive on the marriage market.

[1] Duke John William of Saxe-Gotha was given permission by her brother to court her, but the marriage plans were interrupted after he engaged in a duel with Anders Lagercrona in the presence of the monarch.

Frederick had married her with the intent of reaching the throne, and immediately began plotting to have her named heir in place of her nephew.

On 2 November 1713, she appeared at her first session, and a decision was made to assemble the Riksdag to declare her regent in her capacity as the closest heir to the throne.

It has never been claimed that she had any advance knowledge of the purported involvement of her husband's aide André Sicre, but she did immediately declare herself monarch in Uddevalla by stating that she had inherited the throne.

They gained the support of the Riksdag opposition, who wanted to end the absolute monarchy established in 1680 and reinstate parliamentary rule.

On 15 December 1718, she declared that though she had inherited the throne, she did not intend to keep the Carolinian absolutism but agreed to reinstate the older system.

Ulrika Eleonora was forced into agreeing to abolish absolute monarchy and the right to inherit the throne, both for her and for her contestant, her nephew Charles Frederick, Duke of Holstein-Gottorp.

On 19 February she signed the Instrument of Government (1719), thereby securing the support of the Estates not to give the throne to her nephew and competitor.

Despite the ongoing attack, Ulrika Eleonora forced her courtiers to attend a previously accepted reception at the British ambassador's, "being so untouched as if there had been no enemies present for hundreds of miles",[1] which was considered to be an impressive act of courage.

Her favorite courtier was Emerentia von Düben (1669–1743), her old nurse, who had been ennobled and made lady-in-waiting in 1707 and with whom she had a close relationship all her life.

Horn criticized her for discussing state affairs with her husband, pressed her as to whether she would respect the constitution and insulted her by making the remark that nothing better was to be expected "under the regiment of a female."

Ulrika Eleonora supported the political ambitions of her consort, and from the beginning, she wished for him to become her co-monarch, in the fashion of William III and Mary II.

On 29 February 1720, after having again been denied a co-monarchy, Ulrika Eleonora abdicated in favour of her husband on the condition that she should succeed him if he should die before her.

The reign of her husband began the period traditionally known as the Age of Liberty, when the monarchy lost most of its power to a parliamentary system.

In 1734, Frederick became the first king in Swedish history to have an official mistress, the noblewoman Hedvig Taube, who was given the title Countess of Hessenstein.

Ulrika Eleonora expressed her disapproval to her close confidant Emerentia von Düben,[4] who convinced her never to display any public reaction to the affair, as it would be beneath the queen's dignity and her position was untouchable: "As the Moon travels along its course over the sky without bothering over the barks of dogs, so should Her Majesty despise the gossip, which has been unleashed by this much unfortunate and blinded commitment".

[1] By convincing Ulrika Eleonora not to publicly display her displeasure of his adultery, Emerentia von Düben also became favored by King Frederick.

At the beginning of the affair, on one occasion she even walked publicly with Hedvig Taube in her effort to defend the reputation of her husband.

[6] The policy of Ulrika Eleonora not to express her dislike of Frederick's adultery was weakened during her last years, possibly due to the unique position of Taube as the official mistress, because of the long-term nature of the affair and because they had children.

The king reacted with rage, refused to accept the statement and stated that the Riksdag of the Estates had promised him not to interfere in his private life.

In 1738, she was asked by the Estates to accept the regency at an occasion when Frederick was so ill that he was in danger of dying and was incapable of ruling.

She enjoyed to participate in the dance at court balls, and though religious scruples made her conflicted in the issue, she also engaged German and French theatre companies to perform at Bollhuset.