B2Gold acquired the Masbate Mine, located on Masbate Island, Philippines, through a merger of CGA Mining Limited in January 2013. The deposit is mined by open cut, and current ore processed is a combination of historically stockpiled, low-grade, oxidised material and freshly mined sulfide ore. The comminution circuit consists of a 9.75 m diameter by 3.62 m, 8.5 MW SAG mill followed by 9.6 MW of secondary ball milling. SAG pebble crushing and a three-stage supplementary crushing plant are also used in the grinding circuit. Gold recovery is achieved via a conventional leach/CIP plant. A plant expansion, which included the addition of a third ball mill and crushing circuit upgrades, was commissioned in 2019 to enable an increase from 6.5 Mt/a to 8.0 Mt/a. In 2023 a detailed grinding circuit survey was conducted by the site metallurgical team, with guidance from Metcom Technologies, Inc., to benchmark circuit performance and identify process optimisation opportunities. Bond Work Index analysis was used to benchmark circuit efficiency, and Functional Performance Analysis was used to identify specific performance improvement opportunities in Classification System Efficiency (CSE) and Ball Mill Grinding Efficiency. Drop-weight and rotary mill based comminution tests were conducted on the 2.4 metric ton SAG feed sample which was collected as a composite before and after the slurry samples were collected. Optimal grind size targeting was achieved via grind versus gold recovery laboratory tests on the same SAG feed composite in combination with the results of the grinding survey. This paper describes the detailed, systematic approach utilised in the comminution circuit optimisation process.