We report measurements of bromine monoxide (BrO) and use an observationally constrained chemical box-model to infer total gas phase inorganic bromine (Br<sub>y</sub>) over the tropical Western Pacific Ocean (tWPO) during the CONTRAST field campaign (January–February 2014). The median tropospheric BrO Vertical Column Density (VCD) over the tWPO was measured as 1.6 × 10<sup>13</sup> molec cm<sup>−2</sup>, compared to model predictions of 0.4 × 10<sup>13</sup> in CAM-Chem, 0.9 × 10<sup>13</sup> in GEOS-Chem, and 2.1 × 10<sup>13</sup> in GEOS-Chem with a sea-salt aerosol (SSA) bromine source. The observed BrO and inferred Br<sub>y</sub> profiles is found to be C-shaped in the troposphere, with local maxima in the marine boundary layer (MBL) and in the upper free troposphere. Neither global model fully captures this profile shape. Between 6 and 13.5 km, the inferred Br<sub>y</sub> is highly sensitive to assumptions about the rate of heterogeneous bromine recycling (depends on the surface area of ice/aerosols), and the inclusion of a SSA bromine source. A local Br<sub>y</sub> maximum of 3.6 ppt (2.3–11.1 ppt, 95 % CI) is observed between 9.5 and 13.5 km in air masses influenced by recent convective outflow. Unlike BrO, which increases from the convective TTL to the aged TTL, gas phase Br<sub>y</sub> decreases from the convective TTL to the aged TTL. Analysis of gas phase Br<sub>y</sub> against multiple tracers (CFC-11, H<sub>2</sub>O / O<sub>3</sub> ratio, and θ) reveals a Br<sub>y</sub> minimum of 2.7 ppt (2.4–3.0 ppt, 95 % CI) in the aged TTL, which is remarkably insensitive to assumptions about heterogeneous chemistry. Br<sub>y</sub> increases to 6.3 ppt (5.9–6.7 ppt, 95 % CI) in the stratospheric middleworld, and 6.9 ppt (6.7–7.1 ppt, 95 % CI) in the stratospheric overworld. The local Br<sub>y</sub> minimum in the aged TTL is qualitatively (but not quantitatively) captured by CAM-chem, and suggests a more complex partitioning of gas phase and aerosol Br<sub>y</sub> species than previously recognized. Our data provide corroborating evidence that inorganic bromine sources (e.g., SSA derived gas phase Br<sub>y</sub>) are needed to explain the gas phase Br<sub>y</sub> budget in the TTL. They are also consistent with observations of significant bromide in UTLS aerosols. The total Br<sub>y</sub> budget in the TTL is currently not closed, because of the lack of concurrent quantitative measurements of gas phase Br<sub>y</sub> species (i.e., BrO, HOBr, HBr, etc.) and aerosol bromide. These simultaneous measurements are needed 1) to quantify SSA derived Br<sub>y</sub> aloft, 2) to test Br<sub>y</sub> partitioning, and explain the gas phase Br<sub>y</sub> minimum in the aged TTL, 3) to constrain heterogeneous reaction rates of bromine, and 4) to account for all of the sources of Br<sub>y</sub> to the lower stratosphere.