Electing to bat, Lahore, who now have six points with a win and rained-off game, lost early wickets but Saad Nasim (43) and Umar Akmal (73 not out) stitched a 92-run fifth-wicket partnership to help the side post 164 for five in 20 overs.
If Nasim hit 3 fours and an equal number of sixes in his 26-ball stay then Umar stole the limelight with his match-winning 45-ball knock that was laced with 5 fours and 5 sixes.
Chasing 165 for victory, a winless Dolphins, who are now out of the tournament, managed 148 for nine in their stipulated overs as Robbie Frylinck's unbeaten 63 run effort went in vain.
Mohammad Hafeez's leadership qualities did come under the scanner when Frynlick's blitz took the Dolphins from 93 for 9 to bat out their full quota of overs. Hafeez (2-18) as the off-spinner though, did his bit with the new ball and ended with figures of 2-18.
Left-arm orthodox Mustafa Iqbal (2-21) and leg-spinner Nasim (2-19) also picked up two wickets each as off-spinner Adnan Rasool (1-13) and left-arm pacer Wahab Riaz (1-31) bagged a wicket apiece.
But wicketkeeper-batsman Umar it was, who won the Man of the Match award for his valiant knock after Lahore lost their top-four batsman for just 34 runs.
Dolphins' Frynlick (3-22) was the impact player from the South African side as the medium-pacer hurt the Lions with three wickets, including openers Ahmed Shehzad (6) and Nasir Jamshed (10).
Reigning Indian Premier League (IPL) champions Kolkata Knight Riders have already made it to the semifinals from this group and now Chenai Super Kings, Perth Scorchers and Lahore will fight it out for the second team to book a last-four spot.
Dolphins: Morne van Wyk (capt), Cameron Delport, Cody Chetty, Khaya Zondo, Jonathan Vandiar, Vaughn van Jaarsveld, Keshav Maharaj, Robbie Frylinck, Andile Phehlukwayo, Kyle Abbott, Prenelan Subrayen.
Lahore Lions: Mohammad Hafeez (capt), Nasir Jamshed, Ahmed Shehzad, Umar Akmal, Saad Nasim, Agha Salman, Asif Raza, Wahab Riaz, Mustafa Iqbal, Adnan Rasool, Aizaz Cheema.