The Morne Trois Pitons‐Micotrin volcanic complex on the island of Dominica (Lesser Antilles) emitted a series of plinian eruptions between 18 ka and 9 ka BP. We studied it to constrain magma storage conditions and volatile degassing balances, by comparison with the three previous ignimbrites (~60‐24 ka BP). Volatile concentrations in glass inclusions and mineral‐melt thermobarometry indicate storage at ≤200 MPa (~6‐8 km) and 860‐880°C. The magmas feeding these plinian eruptions were stored at a shallower depth than those that older ignimbrites from the same volcanic complex (~16 km). Close magma composition and similar halogen ratios, however, suggest a common source for the magmas feeding both the plinian eruptions and the ignimbrites. The large eruptive fluxes of F, Cl and Br to the atmosphere (up to 1.4‐2.8 x 10‐1 Mt/km3, 1.5‐4.0 Mt/km3 and 2‐4 x 10‐2 Mt/km3, respectively), estimated by the petrological method, support the potentially important role of volcanic halogens in modifying the chemistry of the atmosphere, though Cl is underestimated here because of buffering in a fluid phase. The behaviour of S, potentially partitioned in the same fluid phase, prevents here the calculation of an eruptive outgassing budget.