The ladies, who play in the Southern Division of the FA Women's Premier League, beat higher-grade Charlton, currently third in the PL National Division, in Sunday's semi-final.
Goals from Jess Cheeseman and Wendy Martin secured a 2-0 win and set-up a final against MSA Ladies at Harrow Borough on Thursday, March 29.
"I was absolutely delighted for the girls, it's a fantastic achievement," said manager Karen Hills, who spent seven successful years as a player at Charlton.
"It's the first time we've reached the final so we'll put in a lot of work and preparation to get it right."
The ladies are back in action in the Premier League Cup against Colchester at Frederick Knight Sports Ground, Tottenham, kick-off 2pm this Sunday.
They are in a tough group and suffered a 2-0 loss at West Ham in their second group match last week.
LONDON FA WOMEN'S CUP, SEMI-FINAL
Spurs Ladies 2-0 Charlton
Spurs Ladies started at a high intensity against Charlton and that proved key to Sunday's fine semi-final victory.
Bianca Baptiste's pace up front caused problems throughout and she carved out the key opening goal, winning possession and delivering an inch-perfect cross for Jess Cheeseman to slot home for 1-0 after 15 minutes.
Charlton struggled to cope with the ladies work-rate and pressing as Wendy Martin and Robyn McEvoy worked tirelessly to win their battles in the central areas.
The second goal followed in the 38th minute as Robyn curled in a corner that Wendy flicked on at the post and the ball sailed home.
Spurs continued to press in the second half and Charlton were restricted to shots from distance comfortably gathered by Jo Ayre.
The introduction of Jenna Schillaci and Derrie O'Halloran maintained the pressure on Charlton and the team saw out the game to deservedly take their place in the final.
"We've had a couple of tough weeks where results haven't gone our way but we turned it around and were worthy winners," added Karen.
Spurs Ladies: Jo Ayre, Miranda Hall, Vicky Elcome, Robin Downier (Ryha Vyse, 83), Sam Pittuck, Wendy Martin, Robyn McEvoy, Jess Cheeseman (Jenna Schillaci, 70), Kirsten Thompson (Derrie O'Halloran, 78), Bianca Baptiste, Emma Sherwood.