Medication management is becoming increasingly challenging for older people, and there is limited evidence to guide medication prescribing and administration for people with multimorbidity, frailty, or at the end of life. Currently, there is a lack of clear research priorities in the field of geriatric pharmacotherapy. To address this issue, international experts from 5 research groups in geriatric pharmacotherapy and pharmacoepidemiology research were invited to attend the inaugural Optimizing Geriatric Pharmacotherapy through Pharmacoepidemiology Network workshop. A modified nominal group technique was used to explore and consolidate the priorities for conducting research in this field. Eight research priorities were elucidated: quality of medication use; vulnerable patient groups; polypharmacy and multimorbidity; person-centered practice and research; deprescribing; methodological development; variability in medication use; and national and international comparative research. The research priorities are discussed in detail in this article with examples of current gaps and future actions presented. These priorities highlight areas for future research in geriatric pharmacotherapy to improve medication outcomes in older people.