Harps were, at this stage, dominating proceedings, but Athlone gradually grew in stature and indeed played the better football for a time and with Stephen Feeney beginning to stamp authority in the middle of the park the St Mel's Park outfit began to look threatening.
The first 45 minutes passed without a goal and at the start of the second half the home side again went close to breaking the deadlock, but Shane Bradley put his effort wide from Jonathan Minnock's teasing free kick.
Harps forced a succession of set-pieces, but couldn't find the killer final touch and this was ultimately to be their downfall.
Michael O'Connor's side pressed hard late on for the winner, but they would find no way past James Gallagher despite forcing a couple of late openings which had the home crowd in an anxious mood heading into the three minutes of added time.
The added time brought nothing in the way of an addition to the score-line and at the conclusion the stalemate remained intact and the sides must now replay for the right to progress to the last eight of the competition.
The replay will take place on Tuesday night next in St.Mel's Park with a 7.30 kick off time.
Both sides will be hopeful that they can up their game for Tuesday night's second game with Harps likely to be without Davitt Walsh, who limped off with a dead leg.
This will certainly curtail their attacking threat although Darren Meenan and Matthew Crossan have been in good form recently and, should Walsh not make it, these two are likely to form the front pairing.
Tuesday will be the start of a busy spell for Harps as they travel to Limerick on Friday night with Cobh Ramblers coming to Finn Park the following Saturday before Shamrock Rovers visit that Tuesday and then on the Friday night Harps will face in-form Dundalk.
Finn Harps: James Gallagher; Sean Mc Gowan, David Bell, Eloka Asokhu, Shane Bradley; Michael Funston, Barry Curran, Jonathan Minnock, Matthew Crossan; Davitt Walsh, Darren Meenan. Subs: Chris Malseed (for Walsh); Ryan McGavigan (for Curran).
Athlone Town: Danny O'Leary; Damien Rushe, Ian Rossiter, Des Hope, Jim Sheridan; Colin Fortune, Stephen Gavin, Stephen Feeney, Padraig Moran; Eric Lavine, Noel McGee. Subs: Alan Kelly (for Rushe); Istavan Lakatos (for McGee).
Referee: Ritchie Winters
Finn Harps Dot Com Man-of-the-Match: Certainly the contenders were few and far between last evening with a large amount of the participants failing to inspire.
The official Carlsberg man-of-the-match was awarded to Athlone midfielder Stephen Feeney and certainly one couldn't find much argument with this decision as the number 8 was probably the most effective player on the park.
For Harps, though, Shane Bradley was once again the best performer and continues to act as a colossus at the heart of the Harps defence. ‘Rita' turned in a typically solid evening at the office last night and almost got on the score-sheet in the second half.