Abstract The Antarctic Peninsula has been climate‐sensitive since the mid‐20th century, but long‐term glacier mass balance data are scarce. This study uses historical aerial and high‐resolution satellite imagery to estimate mass changes on the western Antarctic Peninsula (66°S $66{}^{circ}mathrm{S}$–68°S $68{}^{circ}mathrm{S}$) from 1989 to 2020. Terminus retreat during 1989–2020 led to a mass loss of 687±125 $687pm 125$ Mt a−1 ${mathrm{a} }^{-1}$. During 1989–2016, a minor geodetic mass gain rate of 58±286 $58pm 286$ Mt a−1 ${mathrm{a} }^{-1}$ is found. Frontal surface lowering in this period is offset by higher‐elevation thickening. In contrast, during 2016–2020, a nearly doubling of the frontal thinning and consequently a general surface lowering of 0.06±0.05 $0.06pm 0.05$ m a−1 ${mathrm{a} }^{-1}$ occurred, corresponding to a geodetic mass loss of 447±423 $447pm 423$ Mt a−1 ${mathrm{a} }^{-1}$. At the same time, the zero‐elevation change altitude rose from 500 m to above 600 m. These shifts are coincident with rising atmospheric and oceanic temperatures, suggesting a transition to accelerating mass losses.