The 22-year-old follows former Middlesbrough man Jonathan Grounds in moving to St Andrew's this week as Blues boss Lee Clark focuses on improving his defence.
Birmingham conceded 74 goals in the Championship last term, but managed to avoid relegation on the final day of the campaign, and Clark is hoping that the arrival of Hall will help them shore things up.
There is no option in the agreement for the Lillywhites to recall Hall, who made 34 appearances in a loan spell at League One Swindon Town during 2013-2014.
"I watched him closely at Swindon Town last season and he impressed before picking up a hamstring injury," Clark told the club's official website. "I know that [Swindon manager] Mark Cooper speaks very highly of him and we were actually in for Grant last season but due to the link between Tottenham and Swindon it didn't work out for us.
"We're delighted to have Grant on board and it's no coincidence that my first two signings have been defenders because that was an area we needed to address.
"We simply didn't keep enough clean sheets last season and, as we look to continue to improve that area, there will be more defenders to come."
Hall has yet to make a senior appearance for Spurs since joining from Brighton & Hove Albion in 2012.
