Peter Mattaliano claims his ex-client verbally agreed to hand over 2.5 per cent of his acting salary from all TV and movie roles back in May, 2011, but failed to honour the deal.
Morrison has taken issue with Mattaliano's accusations and is now firing back with a lawsuit, insisting he came up with "this outrageous figure based upon a purported oral agreement", which the 37-year-old denies ever making.
The actor is adamant he paid Peter generously for helping him hone his talents, and he wants a U.S. judge to formally declare Morrison owes nothing to his old coach, reports TMZ.com.
Morrison is also suing Peter for the unauthorised use of his name and image on his website.
The star began his career on Broadway before finding fame on TV musical Glee as Spanish teacher and glee club supervisor Will Schuester in 2009.