Bulgarian singer Dara won the contest with the crowd-pleasing track "Bangaranga," earning 516 points from judges and viewers across Europe.
Israel’s Noam Bettan finished second with 343 points for "Michelle," while Romania's Alexandra Căpitănescu placed third with 296 points for "Choke Me."
Szemplińska scored 150 points overall, including 133 from judges, receiving the maximum 12 points from Lithuania, Germany, Austria and Belgium.
She ranked seventh after the jury vote but dropped to 12th after gaining just 17 points from viewers.
Performing the song "Pray," she delivered a vocal-driven performance blending elements of soul, gospel and hip-hop, accompanied by dancers on a sloping stage.
The Polish jury awarded its top 12 points to Israel, followed by Bulgaria with 10 and Greece with eight.
Edyta Górniak's runner-up finish in 1994 with "To nie ja" remains Poland's best result in the contest.
This year's competition featured contestants from 35 countries. Spain, the Netherlands, Iceland, Ireland and Slovenia boycotted the event in protest against Israel's participation.
Ahead of the final, Austrian police detained 14 pro-Palestinian activists near Vienna's Stadthalle arena, public broadcaster Polish Radio’s IAR news agency reported.
Thousands also took part in an anti-Israel rally under the slogan "No stage for genocide," which police said passed without major incidents.
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Source: TVP, IAR, PAP