This dataset presents thaw front depths (TFD) measurements made in two thermo-erosional gullies on Bylot Island, Nunavut, Canada, from probing to refusal with a graduated steel rod. The first gully, TEG1, formed in 1999 and is still active today (2024). The second gully, TEG2, is a gully that has been stabilized for at least 66 years. TFD was measured in 2017 from 13 June to 29 July, and in 2018 from 12 June to 16 August. Measurements were made every 2-3 days along transects of ~30 points (10 to 30 m in length) perpendicular to the TEG and averaged into three positions: 1) shoulder of the gully (the polygon directly adjacent to the gully), 2) gully slope, 3) gully stream.