To describe and quantify the frequency, velocity and acceleration at impact during tackling in Australian football using a combination of video and athlete tracking technology.Quasi-experimental.Data was collected from twenty professional Australian Football League players during four in-season matches. All tackles made by the player and those against the player were video-coded and time stamped at the point of contact and then subjectively categorised into low, medium and high intensity impact groups. Peak GPS and acceleration data were identified at the point of contact. Two-way analysis of variance was used to assess differences (p<0.05) between tackle type (made and against) and tackle intensity.A total of 173 tackles made and 179 tackles against were recorded. Significant differences were found between all tackle intensity groups. Peak velocity was significantly greater in high (19.5±6.1 k mh(-1)) compared to medium (13.4±5.8 k mh(-1)) and low intensity (11.3±5.0 k mh(-1)) tackles. Peak Player Load, a modified vector magnitude of tri-axial acceleration, was significantly greater in high (7.5±1.7 a.u.) compared to medium (4.9±1.5 a.u.) and low intensity (4.0±1.3 a.u.) tackles.High intensity tackles, although less frequent, are significantly greater in speed of movement immediately prior to contact and in the resultant impact acceleration compared to tackles of lower intensity. Differences in accelerometer data between tackles observed to be progressively greater in intensity suggest a level of ecological validity and provide preliminary support for the use of accelerometers to assess impact forces in contact invasion sports.