Technical Abstract: 'Black Diamond' is a recently developed thornless blackberry cultivar with large fruit size, high yield, and good processed fruit quality that has rapidly become an industry standard. The flavour of 'Black Diamond' fruit is not the same as 'Marion', which is regarded by the industry as having the ideal flavour. In order to understand the aroma differences, the volatile composition of 'Marion' and 'Black Diamond' was analysed using stir bar sorptive extraction-gas chromatography–mass spectrometry (SBSE-GC–MS) and solidphase extraction (SPE)-microvial insert thermal desorption-GC–MS for two growing seasons. Although seasonal variations were present, the overall volatile profile in 'Marion' and 'Black Diamond' were very similar, but the concentrations of some aroma compounds varied greatly. Odour-activity value (OAV) indicated that furaneol, linalool, b-ionone, and hexanal could be most important in 'Marion', while in 'Black Diamond', the most important compounds were linalool, b-ionone, furaneol, and 2-heptanol. The major difference between the cultivars for aroma compounds was that 'Marion' had a 5 times higher OAV of furaneol than 'Black Diamond', while 'Black Diamond' had a 3 times higher OAV of linalool than 'Marion'. The chemical analysis results matched with the descriptive sensory evaluation that 'Marion' had more berry, fruity, strawberry aroma while 'Black Diamond' had more floral aroma.