Courthouses in Diamond Bar, California, the US. Courthouses locations in Diamond Bar, California. Find the nearest courthouses locations, near you. All types of business services Accounting ATM Bank Courthouse Finance Insurance Lawyer Real estate School Travel University All courthouses in Diamond Bar US Inspector General Courthouse +1 909-396-4401 21660 Copley Drive # 370, Diamond Bar, California 91765 Write a review Phone Directions