The 21-year-old, who moved to the Terriers from Oldham Athletic last summer, has played 10 first-team games and kept five clean sheets.
"Joel has shown what a capable young goalkeeper he is," head coach David Wagner said.
"He performed very well every time he came into the team."
Coleman played 45 appearances for Oldham before moving to the John Smith's Stadium for an undisclosed fee.
Goalkeeper Joel Coleman has extended his stay at Huddersfield Town until the summer of 2019, after signing improved contract terms.