BACKGROUNDCold storage of platelets may extend shelf life compared to room temperature storage. This study aimed to investigate in vitro platelet quality and function in cold‐stored and delayed‐cold‐stored nonagitated apheresis platelets in platelet additive solution during storage for 21 days.STUDY DESIGN AND METHODSTen double apheresis platelet concentrates in 37% plasma/63% PAS‐IIIM were split into two groups; nonagitated 2 to 6°C storage (CSPs) and delayed cold storage (DCSPs) with 7 days agitated storage at 20‐24°C followed by nonagitated cold storage for 14 additional days. Platelet count, metabolism, viscoelastic properties, and aggregation ability were measured on Days 1, 7, 14, and 21.RESULTSAll platelet units, both CSPs and DCSPs, complied with the EU guidelines throughout storage for 21 days. Swirling was not detectable after cold storage. Cold storage improved platelet function; however, DCSP on Day 7 showed poorer results compared to CSP. Cold storage slowed down metabolism, with lower lactate and higher glucose concentrations in the CSP compared to the DCSP throughout storage for 21 days.CONCLUSIONCold storage of platelets improved platelet function in in vitro assays, even though delayed cold storage on Day 7 showed poorer results compared to continuous cold storage. This difference could be explained by accelerated metabolism and higher glucose consumption during the period of room temperature storage. Cold storage and delayed cold storage could ease inventory management. Further studies investigating the in vitro and clinical effects of cold‐stored and delayed‐cold‐stored platelets are encouraged.