BACKGROUND: The Western Australian Haemodialysis Vascular Access Classification instrument was developed to classify the cannulation complexity of the arteriovenous fistula or arteriovenous graft as simple, challenging, or complex. Although the instrument was developed by experts in haemodialysis nursing, the instrument had not undergone formal validity or reliability testing. OBJECTIVES: Evaluate the Western Australian Haemodialysis Vascular Access Classification instrument for content validity, interrater and test-retest reliability. DESIGN: Prospective cohort study. PARTICIPANTS: Content validity was assessed by haemodialysis nursing experts (n = 8). The reliability testing occurred in one in-centre and one satellite haemodialysis unit in Western Australia from September to November 2019. Reliability testing was performed by 38 haemodialysis nurses in 67 patients receiving haemodialysis and 247 episodes of cannulation. MEASUREMENTS: Interrater and test-retest reliability assessment was conducted using κ, adjusted κ, Bland-Altman plots, intraclass correlation coefficient and Pearson's correlation coefficient. RESULTS: The final version of the instrument (n = 20 items) had individual item-level content validity indices ranging from 0.625 to 1.00 with a scale-level content validity index of 0.89. For both interrater (n = 172 pairs) and test-retest (n = 101 pairs), most individual variables had excellent adjusted κ (n = 33 variables), some fair to good agreement (n = 6 variables) and one variable with poor agreement. The classification of simple, challenging and complex demonstrated adjusted κ of fair to good, to excellent agreement for interrater reliability with lower levels of agreement for test-retest reliability. CONCLUSIONS: This instrument may be used to match a competency-assessed nurse to perform the cannulation thereby minimising the risk of missed cannulation and trauma.