A statement from Championship rugby side Pirates says they hope the ground will open in September 2019.
In December, club director Colin Groves estimated construction would begin "in the middle" of this year.
National League South side Truro only agreed to share the proposed 6,000-capacity ground with Pirates in April.
The statement said building will "hopefully" start next spring, with work on the stadium on the outskirts of Truro taking 14 months.
Work on the Stadium for Cornwall, to be shared by Cornish Pirates and Truro City, will not start any earlier than spring 2018.