The United States star will be hoping to get first team football with the Championship club. Reading are struggling to stay in the league.
Miazga will be expected to try and shore up their leaky defense.
The 23-year-old was at FC Nantes for the first half of this season.
Reading Chief Executive Nigel Howe said in a statement: "Having already sourced extra quality in the form of a striker, two midfielders and a goalkeeper this month, I'm delighted that Matt now arrives to bolster our defensive ranks for the final 18 games of the season.
"Committed to our cause, I am confident he will be a real asset to the first team dressing room for the remainder of the 2018-19 campaign."