The world number five teamed with Hopman debutant Jerzy Janowicz to beat the US pairing of Serena Williams and John Isner 2-1, atoning for the disappointment of losing last year's final to France.
Radwanska set up the win when she stunned a feisty Serena in the women's singles tie that opened the final, beating the world number one for the first time in nine meetings.
Isner then levelled with a straight-sets win over Janowicz, before the Poles clinched the title in a spirited mixed doubles encounter.
It was a difficult night for Serena, who was aiming to become the first player to win three Hopman Cup titles.
Serena had a heated discussion with the chair umpire over a contentious point in the third set of the doubles and appeared to call the umpire a ‘liar’ before the tournament referee came onto court to resolve the issue.
The 33-year-old then smashed her racquet when she missed a crucial shot on break point in the seventh game of the second set as the Poles pulled away to win the decider, 7-5, 6-3, and deny the US a record seventh title in the tournament's 27-year history.
Radwanska and teammate Grzegorz Panfil were beaten by France's Alize Cornet and Jo-Wilfried Tsonga in the decider last year.
Radwanska delighted with first win over Serena
In the women's singles, Radwanska broke through for the first win of her career over Serena, 6-4, 6-7 (3/7), 6-1, in just over two hours.
Beaten by the American powerhouse in their previous eight meetings, in which Radwanska had only won a single set, she capitalised on the flood of unforced errors by Serena.
The 25-year-old said the result was a great confidence boost ahead of the Australian Open in Melbourne later this month. "I'm just really happy I played my best tennis today [Saturday]," she said. "Of course it doesn't matter what the score is, she [Serena] is a great fighter.”
Isner squared the ledger when he managed to down an inspired Janowicz in straight sets, 7-6 (12-10), 6-4 to level the tie, setting the scene for the doubles decider.
Unfortunately for Serena, who was very inconsistent all tournament, her patchy form continued into the mixed doubles, where her misfiring serve helped the Poles climb back from being down a service break in the first set.
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