The club, which dates back more than a century, has played at the grounds since 2008 after their ground-sharing agreement with Northwood FC ended.
The grounds are owned by KSIMC, who have agreed to extend the club's lease for five years, and included a clause which would extend the lease further if triggered.
Negotiations have been ongoing over the last decade, with Wealdstone FC keen to stay at the ground, retaining exclusive use of the 4,000 capacity stadium and Ruislip Social Club.
They will also continue to have use of the car park for the first five years of the lease.
Chairman of Wealdstone FC, Peter Marsden, said: “I am very pleased we have been able to successfully conclude complex negotiations with KSIMC and we are grateful to them.
"We have established a firm base for our future at Grosvenor Vale and this agreement will enable us to further develop our infrastructure and attract new investment to the club to support our footballing and community ambitions.”