Harmonized Japanese Study on Aging and Retirement (Harmonized JSTAR) is an easy-to-use version of data from three waves of the Japanese Study on Aging and Retirement (JSTAR) with a set of harmonized variables suitable for cross-country analysis. Using the RAND HRS and Harmonized HRS as models, Harmonized JSTAR defines variables as identically as possible with the RAND HRS and Harmonized HRS to allow users to compare variables with all other Harmonized data sets. Documentation for each variable in Harmonized JSTAR, including a description of its creation, the JSTAR variables used, and descriptive statistics, is detailed in the Harmonized JSTAR codebook.