The Super Kings managed to post just 126-9 in their 20 overs after winning the toss and choosing to bat first.
Daniel Sams hit 26* while Devon Conway and Cody Chetty each hit 24. Those were the only Super Kings batsmen to reach double figures as Andrew Tye took 3-32 and Imad Wasim grabbed 2-23 for the Orcas.
Quinton De Kock then led the successful chase for the Orcas with an unbeaten 50-ball 88 including 10 fours and four sixes.
He was well supported by Shehan Jayasuriya who hit 31* as Seattle needed just 15 overs to reach 127-1 and secure a spot in the final.
Their opponents will be determined when the Super Kings face MI New York, who beat the Washington Freedom by 16 runs in the Eliminator on the same day, on Friday.
MI New York made 141-7 off their 20 overs after being put in to bat by the Freedom.
Dewald Brevis, who played because of an injury sustained by Captain, Kieron Pollard, in their last game, led the way with 57 off 41 balls including four fours and three sixes.
Saurabh Netravalkar took 2-25 for the Freedom.
Washington were then restricted to 125-9 from their 20 overs despite 28 from Marco Jansen and 24 from Andries Gous.
Trent Boult led the charge with 4-20 while Nosthush Kenjige took 2-19 for MI New York.
The Orcas restricted their opponents to 144-7 off 20 overs after winning the toss and electing to field.
Akeal Hosein led the way with the bat for the Freedom with an unbeaten 22-ball 33 including a four and a pair of sixes. Earlier, Andries Gous made 28 and Captain, Moises Henriques, made 24 against a pair of wickets, each, from Wayne Parnell and Harmeet Singh.
The Orcas then needed 19.4 overs to reach 148-5 and secure victory. Quinton De Kock led the way with 48 off 37 balls including three fours and as many sixes. All-rounder, Imad Wasim, finished unbeaten on 43 from 38 balls. Shimron Hetmyer contributed 23.
The day started with the Orcas making a respectable 183-9 off their 20 overs after being put in to bat by Pooran.
The bulk of their scoring was done by South African superstar, Quinton De Kock.
The opener, fresh off 88* in Qualifier 1 against the Texas Super Kings on Thursday to help the Orcas advance to the final, made a 52-ball 87 including nine fours and four sixes on Sunday.
He was supported well by Shubham Ranjane and Dwaine Pretorius who had scores of 29 and 21, respectively. Pretorius’ knock came off just seven balls and included three fours and a six.
Rashid Khan was, as usual, brilliant with the ball for MI New York with 3-9 from his four overs while Trent Boult took 3-34 from his four over spell.
MI New York’s chase got off to a rough start when Steven Taylor was bowled by Imad Wasim for a duck in the first over but then, the Pooran show started.
In what was a magnificent knock, the left-hander from Trinidad hit 10 fours and 13 sixes on his way to a 55-ball 137* to lead his team to victory. His fifty came up off just 16 balls while his century took 40 balls.
Dewald Brevis was the next highest scorer with 20 as MI New York needed just 16 overs to reach 184-3 and put themselves down in the history books as the first ever champions of Major League Cricket.
Pooran ended the tournament as the leading run scorer with 388 runs in eight matches at an average of 64.66. He was also named as the tournament MVP.
His MI New York teammate, Trent Boult, topped the leading wicket-taker list with 22, 11 more than anybody else.
After winning the toss and electing to field first, the MI New York bowlers dominated the Orcas batting, restricting them to 108 all out off 19.1 overs.
Shubham Ranjane (35), Harmeet Singh (20) and Aaron Jones (12) were the only batsmen to reach double figures for the Orcas against 3-22 and 3-25 from eight overs combined from superstars Rashid Khan and Trent Boult, respectively.
Captain Kieron Pollard also chipped in with 2-11 from his 2.1 overs.
It then took MI New York only 14.2 overs to reach 111-4 with Pooran finishing 62* off 37 balls, his 41st T20 half-century.
His knock included seven fours and two sixes.
Full Scores:
Seattle Orcas 108 all out off 19.1 overs (Shubham Ranjane 35, Rashid Khan 3-22, Trent Boult 3-25)
MI New York 111-4 off 14.2 overs (Nicholas Pooran 62*, Cameron Gannon 2-40)
