Background As the first contact for any health‐related need, primary care clinicians often address multiple patient problems, with a range of possible outcomes. There is currently no patient‐reported outcome measure (PROM) which covers this range of outcomes. Therefore, many research studies into primary care services use PROMs that do not capture the full impact of these services. Objective The study aim was to identify outcomes sought by primary care patients which clinicians can influence, thus providing the basis for a new primary care PROM. Methods We used a Delphi process starting with an outcomes list inductively derived in a prior qualitative study. Thirty‐five experts were recruited into patient, clinician and academic panels. Participants rated each outcome on whether it was (i) relevant to health, (ii) influenced by primary care and (iii) detectable by patients. In each round, outcomes which passed/failed preset levels of agreement were accepted/rejected. Remaining outcomes continued to the next round. Results The process resulted in a set of outcomes occupying the domains of health status, health empowerment (internal and external), and health perceptions. Twenty‐six of 36 outcomes were accepted for inclusion in a PROM. Primary care having insufficient influence was the main reason for exclusion. Conclusions To our knowledge, this is the first time PROM outcomes have been agreed through criteria which explicitly exclude outcomes less relevant to health, uninfluenced by primary care or undetected by patients. The PROM in development covers a unique set of outcomes and offers an opportunity for enhanced research into primary care.