After a dramatic shootout success on Wednesday that saw their goalkeeper save two spot-kicks before converting the winner, Galway fell short in their second game of twelve-yard roulette.
Galway took the lead early in the second half through an own goal but Sligo-Leitrim roared back through Kailan Barlow of Merville United.
Going into sudden death spot-kicks, Sligo-Leitrim held their nerve and booked a place in Friday's final.
The DDSL entertained Cork in the other semi-final - a matchup that saw two heavyweights cancel each other out in the opening half.
However, Belvedere's Ben McCormack and St Joseph's Boys' Darragh Lynch put the game beyond the Leesiders with two second half goals.
The DDSL have yet to concede a goal in the competition and will be strong favourites to grab their 31st Kennedy Cup title.
Tomorrow's final kicks off at 2pm.
RESULTS
Trophy:
Mayo 4-0 Drogheda
Kilkenny 1-1 NEC SL (Kilkenny won 4-2 on penalties)
Inishowen 3-1 Roscommon District
WWEC 2-2 Limerck County (WWEC won 10-9 on penalties)
Drogheda 0-0 NEC SL (Drogheda won 4-2 on penalties)
Inishowen 5-1 WWEC
Roscommon District 1-1 Limerick County (Limerick County won 4-3 on penalties)
Shield:
West Cork 0-0 Clare (West Cork won 4-2 on penalties)
CMUL 0-3 Kerry
South Tipperary 0-1 Wexford
Carlow 0-1 Longford
Cavan-Monaghan 0-2 Clare
Wexford 2-1 Longford
South Tipperary 1-2 Carlow
Plate:
Kildare 0-2 Limerick Desmond
NDSL 1-0 Athlone
Kildare 2-1 Athlone
Bowl:
Waterford 0-0 Midlands (Midlands won 8-7 on penalties)
SDFL 0-1 Dundalk
Donegal 1-3 North Tipperary
Wicklow 1-5 Limerick District
SDFL 1-2 Waterford
Limerick District 2-1 North Tipperary
Wicklow 0-1 Donegal
Cup:
Sligo-Leitrim 1-1 Galway (Sligo-Leitrim won 10-9 on penalties)
Cork 0-2 DDSL
Full details are available at: http://www.sfai.ie/index.php/umbro-kennedy-cup and highlights are available on the SFAI Facebook page.