The 23-year-old removed West Indian Dwayne Bravo with the second ball of the 19th over followed by the wickets of countryman Zohaib Khan and another Caribbean player, Kevon Cooper, to finish with 3-27 in his four overs.
His hat-trick restricted a star-studded Lahore team to 125-8 which Karachi Kings overhauled in 15.5 overs for a seven-wicket win.
“I am feeling great,” Amir told AFP. “With every game I am getting into my rhythm and it’s great for me as well as for Pakistan.”
Amir returned to international cricket in January, playing in the three-game Twenty20 series against New Zealand after completing a five-year ban in September last year.
Amir, along with Salman Butt and Mohammad Asif, was banned on charges of arranging deliberate no-balls during the Lord’s Test against England in 2010.
Amir took an impressive 86 wickets in four-day and Twenty20 domestic matches, which forced the selectors to include him on the tour of New Zealand.
The Pakistan Cricket Board is hosting its inaugural Twenty20 league with five teams competing at the neutral venues of Dubai and Sharjah.
The league ends on February 23.