The Leinster U-20s will now face the winners of Ulster / Munster in the Interprovincial Series final in Athlone next Saturday after defeating Connacht 30-10 in the Sportsground today.
Trailing 10-0 in the first half against a strong wind after an Alan Gaughan try - converted by Aidan Wynne who also added a penalty - Leinster then lost lineout jumpers Conor McInerney and Tom Walsh to injury.
But the Blues, who have already defeated both Munster (57-8) and Ulster (24-15) in this year's series, fought back strongly and scored four tries in all.
Both Dublin University wing Shane Monaghan and UCD substitute scrum-half Paul O'Donohoe touched down with prop Cian Healy bagging a brace of tries, bringing his tally to three in a week.
Out-half Brian Collins added two penalties and two conversions to cap a gritty win by Leinster.
“It was a courageous display when you consider that we were down by ten points and had lost the services of two lineout jumpers,” said Leinster manager Philip Orr.
“At one stage we had a prop playing second row and our reserve hooker on in the backrow but we came back strongly and showed immense character. The lads are delighted with the win and we're all looking forward to next weekend's final.”
Connacht Scorers: A. Gaughan (1 try), A. Wynne (1 penalty, 1 conversion)
Leinster Scorers: C. Healy (2 tries), S. Monaghan / P. O'Donohoe (1 try each), B. Collins (2 penalties, 2 conversions).