We dominated the first half at the Olympic Stadium in Athens and deserved our half-time lead after Michael Dawson glanced home Tom Huddlestone's free-kick.
However, Panathinaikos improved in the second half and asked us a few questions, eventually equalising in the 77th minute.
That means we have two points from two matches in Group J with back-to-back games against Maribor to follow. We travel to Slovenia in Matchday Three on Thursday, October 25.
Andre Villas-Boas made three changes to the team that started Saturday's famous win at Old Trafford.
Hugo Lloris took over from Brad Friedel in goal, Dawson returned in place of William Gallas and captained the team and Tom Huddlestone came in for Sandro in central midfield.
It was Huddlestone's first start since our Europa League play-off, second leg against Hearts back on August 25, 2012.
It was clear from the first whistle that the pace of Gareth Bale and Aaron Lennon combined with our movement was going to ber a problem for the home side.
Bale took just two minutes to burn past right-back Giourkas Seitaridis and that led to the first chance of the match. His cross was cleared for a corner and from the corner, Steven Caulker rose to head back into the danger area. There was a suspicion of handball as Panathinaikos cleared their lines.
We controlled the half but it took until the 21st minute for the first serious attempt at goal as Clint Dempsey's free-kick from fully 30 yards curled inches wide.
Dempsey was there again as goalkeeper Orestis Karnezis got away with palming Jermain Defoe's cross back into play, the ball just evading the US international.
Panathinaikos' best moment came in the 31st minute as Quincy Owusu-Abeyie played a clever pass inside Walker for Christodoulpoulos, but Lloris read it all the way and slid out to collect.
We took the lead in the 35th minute. Huddlestone curled in a free-kick from the left touchline and Dawson rose at the near post to glance his header beyond Karnezis and home.
Karnezis did well to keep us at bay before the break. His first save was somewhat unconventional with his right leg as Bale let rip from 25 yards, his second much better, sharply down to his right to palm away after Huddlestone connected sweetly with a half-volley 20 yards out.
Ibrahim Sissoko joined the action in place of Marinos at the interval and Panathinaikos were much improved in the second half.
There was more rhythm to their play and a threat as first Owusu-Abeyie got to the left byline, forcing Dawson to slide clear and then Sissoko looked to burst through centrally before Walker's fine challenge.
In-between, Dempsey sent Defoe away down the right but the striker lashed over from 16 yards.
Dempsey tested Karnezis down to his right in thr 58th minute and Bale fired just wide from the edge of the box as we looked for a second goal.
Gylfi Sigurdsson replaced Dempsey in thr 67th minute and Defoe saw another effort zip just wide, this time after deflecting off Vyntra.
As is always the case, 1-0 is such a slender advantage and Panathinaikos hit back in the 77th minute.
Seitaridis played a clever pass between Steven Caulker and Dawson, Toche ran onto it and tucked the ball past Lloris.
Andros Townsend was soon in the action, followed by Sandro but that final clear-cut chance proved elusive.
Panathinaikos (4-1-2-3): Karnezis, Seitaridis, Triantafyllopoulos, Pinto, Vyntra; Vitolo; Zeca, Marinos (Sissoko, 46); Christodoulopoulos (Mavrias, 85), Toche, Owusu-Abeyie (Chouchoumis, 90+3). Unused subs: Kotsolis, Fornaroli, Barbarouses, Lago.
Spurs (4-2-3-1): Lloris; Walker, Caulker, Dawson, Vertonghen; Dembele, Huddlestone (Sandro, 81); Lennon (Townsend, 76), Dempsey (Sigurdsson, 67), Bale; Defoe. Unused subs: Cudicini, Gallas, Falque, Mason.
Goals: Panathinaikos - Toche (77). Spurs - Dawson (35).
Yellow cards: Panathinaikos - Vyntra (74). Spurs - Bale (40), Townsernd (90).
Referee: Mr F Meyer (Germany).