A phase‐sensitive radar (ApRES) was deployed on Totten Ice Shelf to provide the first in situ basal melt estimate at this dynamic East Antarctic ice shelf. Observations of internal ice dynamics at tidal time scales showed that early arrivals from off‐nadir reflectors obscure the true depth of the ice shelf base. Using the observed tidal deformation, the true base was found to lie at 1,910–1,950‐m depth, at 350–400 m greater range than the first reflection from an ice‐ocean interface. The robustness of the basal melt rate estimate was increased by using multiple basal reflections over the radar footprint, yielding a melt rate of 22 ± 2.1 m a−1. The ApRES estimate is over 40% lower than the three existing satellite estimates covering Totten Ice Shelf. This difference in basal melt is dynamically significant and highlights the need for independent melt rate estimates using complementary instrumentation and techniques that rely on different sets of assumptions. Plain Language Summary Observations of the rate of melting at the base of ice shelves are needed to model accurately ice sheet evolution. Local measurements are scarce, yet necessary for validation of satellite products and ocean models. We deployed a phase‐sensitive radar in the proximity of grounding zone of Totten Ice Shelf in East Antarctica, to measure basal melt in this dynamic region where uncertainties on melt rate estimates are high. We developed a method that accounts for basal geometry complexities and derived a melt rate estimate of ∼22 m per year, which is lower than previous estimates, but it confirms that the basal melt rate Totten Ice Shelf experiences is unusually high for East Antarctica. Key Points First in situ radar‐derived basal melt estimate on Totten Ice Shelf yields 22 ± 2.1 m a−1, at least 40% lower than existing satellite estimates Radar‐derived observation of tidal ice dynamics constrains estimate of ice thickness for a complex base The use of multiple basal reflections in melt derivation increases robustness of the estimate when early off‐nadir returns are present