Nick Dasovic, Allan Preston and George O'Boyle scored the goals for Sandy Clark's men on a memorable evening for the Perth club at Easter Road.
Saints faced Rangers in the final at Celtic Park but were beaten 2-1 by Dick Advocaat's side and are aiming to go on and lift the trophy for the first time this season.
😇 In 1998 the Saints defeated a side from Edinburgh to book their place in the League Cup Final...
— SPFL (@spfl) January 19, 2021
👀 Could history repeat itself on Saturday?#SPFL | @StJohnstone pic.twitter.com/8IjZrqJVHJ