Spurs' impressive run saw them climb up the table from fourth to second, where they are currently five points behind Leicester City with nine games remaining.
Forster, who beat Willian, Harry Kane and Jamie Vardy to win the award, kept three clean sheets during last month, shutting out Arsenal, West Ham United and Swansea.
The 27-year-old also becomes the first goalkeeper to win the award since Tim Krul did so with Newcastle United in November 2013.
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"It's obviously fantastic to win the award, but it's just another incentive to keep working hard and work as hard as I can until the end of the season," Forster, who returned from a long-term injury in January, told the club's website (www.saintsfc.co.uk).
"I think it was a good month all round. We put in a lot of good performances as a team with a good run of clean sheets. If you're doing that then it's easier to win games."
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by John O'Brien)
