The actor revealed the news on his Twitter page today (April 24), confirming that show bosses have chosen to write out his character.
Alderton told fans that the decision was made due to Patsy Palmer's upcoming departure as Terry's on-off girlfriend Bianca Butcher.
He said: "So, I'm leaving EastEnders in July. Unfortunately Patsy leaving has changed things in the story. It's very sad but it's been a great ride."
Alderton also joked that the news is likely to rule Terry out as Lucy Beale's killer as the whodunnit storyline isn't expected to be resolved until February.
Good news is I have live gigs!!! http://t.co/dO9uxZpJ0V is the place for info. Thanks for the support in the show. It tells you one thing...— Terry Alderton (@TerryAlderton) April 24, 2014
Terry Spraggan's not the killer! X— Terry Alderton (@TerryAlderton) April 24, 2014
Or is he?... :@)— Terry Alderton (@TerryAlderton) April 24, 2014
Palmer announced her plans to quit EastEnders earlier this month, but she will remain on screen until the autumn.
Alderton started filming at the BBC soap in September last year and appeared on screen from November, when Bianca introduced Terry to her family as her new boyfriend.
The 43-year-old was the first signing of EastEnders' current executive producer Dominic Treadwell-Collins after he took office at the show last summer.
Digital Spy Soap Scoop video - hit play below for gossip on Coronation Street's mini-bus crash aftermath, Shabnam's secret being revealed in EastEnders, a terrible accident in Emmerdale and a shock arrest in Hollyoaks.