The side headed to Alloa’s Indodrill Stadium to play-off against Rossvale for a place in next season’s SWFL 2.
The Fifers finished second in the Scottish Women's Championship North, enough to see them enter a play-off for a place in the second tier.
The final was always likely to be a tense affair and so it proved.
The Fifers took the lead on the 20 minute mark, only for Rossvale to soon grab a deserved equaliser seven minutes later.
But East Fife responded well to seeing their opponents pull level and managed to retake the lead with 62 minutes gone.
Rossvale piled on the pressure as they looked to get level again for a second time, only for the Fifers to net their third, and win promotion, with five minutes left on the clock.
Team manager Liz Anderson said post-match that the team were “buzzing” following their win.
East Fife now join title winners Montrose in the SWPL 2 next season.
The club’s under 20s side also continue to impress on the park and, at the time of writing, were sitting seventh in the Lowland Development League Conference A with two matches to play.
East Fife FC chairman Jim Stevenson described their progress as “remarkable” given the bulk of the squad are under 18.
Stevenson added: “A huge credit must be given to Steve Batty and his team for the development of the squad.
"The date for their final home match against Broomhill is still to be confirmed but I’d encourage all supporters to come to Bayview to support the boys.
"Any changes to the U20s squad ahead of next season will be announced following the conclusion of their season.
"The club also entered the Scottish FA Youth Cup Under 18s for the first time this season and we were handed a very difficult first round tie against Celtic.
"This was the first time many of the boys had played with linesmen let alone in front of a crowd of over 500.
"The team gave a good account of themselves against their much more experienced opponents but were knocked out in the opening round.”