Seagoe raced into a two-goal lead but had penalty kicks to thank for Marshall Cup success at the close of play.
A superb start resulted in Seagoe moving ahead thanks to Dylan Byrne’s finish off a clever Gareth Kerr pass.
Kerr’s inventive long-range lob then increased the advantage at the expense of the exposed goalkeeper.
However, Banbridge Town AFC entered the interval on levels terms courtesy of a strong finish to the first half.
Stephen Duke tested the Town goalkeeper from distance before Jasir Silva was left frustrated on his debut by a last-gasp Banbridge block.
Chris Megaw’s shot then bounced off the underside of the crossbar, with Seagoe appeals for a goal waved away before extra-time.
Extra-time failed to produce a decisive moment - turning, as a result, the focus to a spot-kick lottery.
Philip McCoy pulled off an early save before Stephen Duke, Byrne, Kyle McMullen, Geoff McCollum and Stuart Corkin slotted home.
“We can take heart from getting the win despite losing a 2-0 lead,” said Matthew Wright, manager of Seagoe. “I think we have a young group but the squad is constantly improving, with help from my assistant Lee Winter.
“Gareth, Alan Humphries and Stuart were our best players against Banbridge Town AFC.
“We need to focus on putting results beyond teams with 90 minutes of concentration.
“We were without Andy Gordon going into the tie, however, plus lost Sam Nesbitt from the warm-up, so that did not make life any easier for us.
“Both teams put out young squads.”
RESULTS: Mid-Ulster League Division Three - Caledon Rovers 5 Union Lusa 2; Mid-Ulster Reserve League Division Four - Knockmenagh Swifts 2 Windmill Stars 1.