Most Asian countries have employed Chinese medicine (CM) and Western medicine to treat lumbar spinal stenosis (LSS). Evidence synthesis and comparison of effectiveness are difficult since outcomes examined and presented through trials possess heterogeneity. This study aimed to solve the outcome problems for CM clinical trials in LSS by building a core outcome set (COS).To achieve an agreement on a set of core outcome domains, a four-phase study was carried out. First, we identified candidate outcome domains by systematically reviewing trials. In addition, we identified outcome domains associated with patients by conducting semistructured interviews with patients. Next, outcome domains were processed through a national two-round Delphi survey, in which 18 patients and 21 experts were recruited. Finally, the above domains were converted as a core outcome domain set based on a consensus meeting, in which 24 stakeholders were recruited.Seventeen outcome subdomains were identified by the systematic review and interviews. The Delphi survey assigned a priority to four outcome domains in the first round and four outcomes additionally in the second round. The core outcome domains were determined through discussion and redefinition of outcomes in the consensus meeting: pain and discomfort, health-related quality of life, lumbar function, activities of daily living, measures of walking, patient global assessment, adverse events and CM-specific outcomes.COS-CM-LSS is likely to enhance the consistency of outcomes reported in clinical trials. In-depth research should be conducted for the exploration of the best methods to examine the above outcomes.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.