Posh boss Darren Ferguson has been keen to bolster his midfield, with winger George Boyd poised to complete a deadline day move to Nottingham Forest.
Pritchard, 20, has impressed for Tottenham's youth and reserve sides this season but has yet to make a first-team appearance.
His contract expires at the end of the campaign and although Tottenham have previously indicated they will offer him a new deal, the player himself is ensure over his future.
Reports earlier this week suggested Liverpool were interested in signing Pritchard, though his immediate future now lies at London Road.
Speaking via his Twitter account MacAnthony confirmed the youngster had signed on with Posh until the end of the campaign.
"Delighted to announce loan signing of Alex Pritchard from Spurs who has joined until end of season. He is a fantastic young talent," he said.
"Myself & Gaffer watched this young lad destroy our reserve team couple weeks ago scoring four goals from playing left wing/Right wing /att mid."
Meanwhile, midfielder Ryan Mason has been loaned to Ligue 1 club Lorient for the remainder of the season.
Mason has made only three appearances from the bench for Spurs this season, although he has netted eight goals in 10 games for the U21s.
And Davide Petrucci has extended his loan at Peterborough until the end of the season from Manchester United.