The so-called “Kobe Process,” a series of informal joint meetings of the tuna Regional Fishery Management Organizations, has identified a number of issues that should be analyzed in order to improve harmonisation globally. The process identified harmonisation of bycatch data collected by the RFMOs as one such issue. This document is a report of a meeting of technical experts in tropical tuna purse-seine fisheries observer programs, which provided the first opportunity for progress towards harmonisation of bycatch data for tropical tuna purse-seine fisheries. The objective of this meeting was to harmonize data collection systems and variable definitions to improve research on bycatch mitigation, stock assessment and other topics. The report includes recommendations for the minimum data standards and data fields, including identification of areas where some uncertainty in data definitions remains.