Study Design Clinical measurement. Background The Lysholm score and Tegner activity scale are frequently used patient-reported instruments to determine the functional status and activity level after anterior cruciate ligament (ACL) reconstruction. Objectives To translate and cross-culturally adapt the Lysholm score and Tegner activity scale for use in the Dutch population and to evaluate the reliability and validity of these questionnaires in individuals after ACL reconstruction. Methods The translation and adaptation were conducted in several steps according to the guidelines in the literature. The measurement properties of the Lysholm score and Tegner activity scale (internal consistency, construct validity, and floor and ceiling effects) were tested in 96 patients. Reproducibility was tested in 69 patients with ACL injuries. On the first occasion, the International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC) and RAND 36-Item Health Survey (RAND-36) were also administered. Results The Lysholm score and Tegner activity scale showed good test-retest reliability between repeated measures (intraclass correlation coefficient = 0.93 and 0.97, respectively) and reasonable to good internal consistency (Cronbach α = .70-.83). The Lysholm score had a very strong correlation with the IKDC (r = 0.83, P<.01) and moderate correlation with the RAND-36 (r = 0.55, P<.01). The Tegner activity scale had moderate correlations with both the IKDC (r = 0.42, P<.01) and RAND-36 (r = 0.48, P<.01). Conclusion The psychometric performance of the Lysholm score and the Tegner activity scale as outcome measures for Dutch patients after ACL reconstruction is acceptable. J Orthop Sports Phys Ther 2016;46(11):976-983. Epub 28 Sep 2016. doi:10.2519/jospt.2016.6566.