The compound is typically prepared by heating thin layers of urea, the thin layers facilitating escape of ammonia:
:3 (HN)CO   →   [HNC(O)NH]CO  +  2 NH
It can also prepared by treatment of urea with phosgene:  
:2 (HN)CO  +  COCl  →   [HNC(O)NH]CO  +  2 HCl
A similar synthesis employs urea and dimethyl carbonate with potassium methoxide as a catalyst:  
:2 (HN)CO  +  CO(OCH)  →   [HNC(O)NH]CO  +  2 MeOH
The original synthesis entailed oxidation of uric acid with hydrogen peroxide.
Triuret is a complicating by-product in the industrial synthesis of melamine from urea.