Sirk got 64 points to achieve Slovenia's best placement since 2011, when Maja Keuc, who announced the Slovenian expert jury votes this time, was 13th.
The 28-year-old singer-songwriter was a surprise entry in the final in Lisbon since she had a very low ranking until she staged a surprise in the semi-final by inserting an unexpected intermission in her performance.
She repeated the same trick in the finals, only this time inviting the audience to sing along instead of pretending that the silence was a glitch.
Sirk got 41 points from national juries and 23 from televoting.Israel's winning entry
The Lisbon venture was not the first time the classically trained flautist performed in Europe's biggest song contest.
She participated twice before as a backing vocalist for Slovenia, the first time with Tinkara Kovač in 2014 and then in 2016 with Manuella in 2016.
Slovenia achieved the best Eurovision result in 1995, when Darja Švajger finished 7th. Nuša Derenda repeated her feat in 2001.