The paper presents the development of an Older Adult Compendium of Physical Activities (OA Compendium), which aims to estimate the energy costs of physical activities (PAs) in adults aged 60 and older. The authors conducted a systematic literature review and identified 68 articles reporting energy expenditure data on 427 PAs. From these, they derived 99 unique Specific Activity codes with corresponding metabolic equivalent of task (MET60+) values, adjusted for the lower resting metabolic rate (RMR) in older adults (2.7 mL/kg/min). The OA Compendium uses a 7-digit coding scheme, with the last two digits indicating the category for older adults (60+). The MET60+ values are intended to provide more accurate estimates of PA energy costs in older adults, enhancing research and practice in PA assessment and prescription. The authors emphasize the need for further research to validate the MET60+ values and to account for individual differences in RMR and activity intensity. The OA Compendium is available online at https://pacompendium.com.The paper presents the development of an Older Adult Compendium of Physical Activities (OA Compendium), which aims to estimate the energy costs of physical activities (PAs) in adults aged 60 and older. The authors conducted a systematic literature review and identified 68 articles reporting energy expenditure data on 427 PAs. From these, they derived 99 unique Specific Activity codes with corresponding metabolic equivalent of task (MET60+) values, adjusted for the lower resting metabolic rate (RMR) in older adults (2.7 mL/kg/min). The OA Compendium uses a 7-digit coding scheme, with the last two digits indicating the category for older adults (60+). The MET60+ values are intended to provide more accurate estimates of PA energy costs in older adults, enhancing research and practice in PA assessment and prescription. The authors emphasize the need for further research to validate the MET60+ values and to account for individual differences in RMR and activity intensity. The OA Compendium is available online at https://pacompendium.com.