Spurs have a ten-year deal with the NFL to host at least two regular season games every year.
The stadium was due to host an International Series game between the Seattle Seahawks and Oakland Raiders earlier this year, but the fixture was moved to Wembley because of construction delays.
When finished, the ground will feature an artificial surface specifically designed for American football, with a retractable grass pitch being used for soccer.
The megastore was opened on Tuesday by former NFL players and stars of the BBC's NFL Show, Jason Bell and Osi Umenyiora, and will sell a range of apparel and merchandise from all 32 of the league's teams.
In October, Umenyiora told Standard Sport that he believed Spurs' new ground was "absolutely" the most likely home for a future London franchise.
"I think [Tottenham] know exactly what's going to happen here as far as the NFL is concerned," Umenyiora said. "The NFL has invested a huge sum of money in this market, to expand into this market, and if you know anything about the NFL, you know that they're not in to wasting money.
"So the fact that they did that, lets you know what their plans are and Tottenham are on board with those plans."
