We previously demonstrated that microcrystal electron diffraction (MicroED) can be used to determine atomic-resolution structures from vanishingly small three-dimensional crystals. Here, we present an example of an experimentally phased structure using only MicroED data. The structure of a seven-residue peptide is solved starting from differences to the diffraction intensities induced by structural changes due to radiation damage. The same wedge of reciprocal space was recorded twice by continuous-rotation MicroED from a set of 11 individual crystals. The data from the first pass were merged to make a "low-dose dataset." The data from the second pass were similarly merged to form a "damaged dataset." Differences between these two datasets were used to identify a single heavy-atom site from a Patterson difference map, and initial phases were generated. Finally, the structure was completed by iterative cycles of modeling and refinement.