Measurement of ankle joint dorsiflexion is routinely undertaken by clinicians who manage lower limb musculoskeletal pathology. This study aimed to determine the reliability of a technique to measure ankle joint dorsiflexion in a weightbearing position with the knee extended. Four raters with varying clinical experience measured ankle joint dorsiflexion in a weightbearing position with the knee extended on 30 asymptomatic participants. Measurements occurred on two occasions, 1 week apart using (i) a digital inclinometer and (ii) a clear acrylic plate apparatus. Intraclass correlation coefficients (ICCs) and 95% limits of agreement (LOAs) were calculated. Intra-rater reliability of the experienced raters was high for both the digital inclinometer (average ICC=0.88, average 95% LOA=-6.6 degrees to 4.8 degrees ) and the clear acrylic plate apparatus (average ICC=0.89, average 95% LOA=-7.2 degrees to 4.3 degrees ). Intra-rater reliability of the inexperienced rater was good to high for both the digital inclinometer (ICC=0.77, 95% LOA=-9.1 degrees to 8.3 degrees ) and the clear acrylic plate apparatus (ICC=0.89, 95% LOA=-8.1 degrees to 4.6 degrees ). Inter-rater reliability was high for both the digital inclinometer (ICC=0.95, 95% LOA=-5.7 degrees to 5.7 degrees ) and the clear acrylic plate apparatus (ICC=0.97, 95% LOA=-4.7 degrees to 4.7 degrees ). Measurements of ankle dorsiflexion in a weightbearing position with the knee extended can be performed reliably by experienced and inexperienced raters. However, the reliability of this measurement technique needs to be interpreted in the context of the purpose for which the measurement is intended.