<p>Biogenic volatile organic compounds (BVOCs) emitted by plants represent the largest source of non-methane hydrocarbon emissions on Earth. Photochemical oxidation of BVOCs represents a significant pathway in the production of secondary organic aerosol (SOA), affecting Earth’s radiative balance. Organic nitrates (RONO<sub>2</sub>), formed from the oxidation of BVOCs in the presence of NO<sub>x</sub>, represent important aerosol precursors, and affect the oxidative capacity of the atmosphere, in part by sequestering NO<sub>x</sub>. In the aerosol phase, RONO<sub>2</sub> hydrolyze to form nitric acid and numerous water-soluble products, thus contributing to an increase in aerosol mass. However, only a small number of studies have investigated the production of RONO<sub>2</sub> from •OH oxidation of terpenes, among those, few have studied their hydrolysis. Here, we report a laboratory study of OH radical-initiated oxidation of β-ocimene, an acyclic, triolefinic monoterpene released during the daytime from vegetation, including forests, agricultural landscapes, and grasslands. We conducted studies of the OH radical oxidation of β-ocimene in the presence of NOx using a 5.5 m<sup>3</sup> all-Teflon photochemical reaction chamber, during which we quantified the total (gas- and particle-phase) RONO<sub>2</sub> yield and the SOA yields. We sampled the organic nitrates produced and measured their hydrolysis rate constants at different solution pH. The total organic nitrate yield was determined to be 33(±7) %, consistent with the available literature regarding the dependence of organic nitrate production (from RO<sub>2</sub> + NO) on carbon number. We found the hydrolysis rate constants to be highly pH-dependent, with a hydrolysis lifetime of 51(±13) min at pH = 4, and 24(±3) min at pH = 2.5, a typical pH for deliquesced aerosols. We also employed high-resolution mass spectrometry for product identification, which is used to infer key mechanisms of gas–particle partitioning. The results indicate that the ocimene SOA yield under relevant aerosol mass loadings in the atmosphere is significantly lower (< 1 %) than reported yields from cyclic terpenes, such as α-pinene, likely due to alkoxy radical decomposition and formation of smaller higher-volatility products. This is also consistent with the observed lower particle-phase organic nitrate yields of β-ocimene, 1.5(±0.5) %, under dry conditions. We observed the expected hydroxy nitrates by chemical ionization mass spectrometry (CIMS), and some secondary production of the di-hydroxy di-nitrates, likely produced by oxidation of the first-generation hydroxy nitrates. Lower RONO<sub>2</sub> yields were observed under high relative humidity (RH) conditions, indicating the importance of aerosol-phase RONO<sub>2</sub> hydrolysis under ambient RH. This study provides insight into the formation and fate of organic nitrates, ocimene SOA yields, and NO<sub>x</sub> cycling in forested environments from daytime monoterpenes, which are not currently included in atmospheric models.</p>