Objective The aim of this study was to investigate the effect of different mechanical behaviour of the brachial artery on blood pressure (BP) measurements during cuff inflation and deflation. Methods BP measurements were taken from each of 40 participants, with three repeat sessions under three randomized cuff deflation/inflation conditions. Cuff pressure was linearly deflated and inflated at a standard rate of 2–3 mmHg/s and also linearly inflated at a fast rate of 5–6 mmHg/s. Manual auscultatory systolic and diastolic BPs, and pulse pressure (SBP, DBP, PP) were measured. Automated BPs were determined from digitally recorded cuff pressures by fitting a polynomial model to the oscillometric pulse amplitudes. The BPs from cuff deflation and inflation were then compared. Results Repeatable measurements between sessions and between the sequential order of inflation/deflation conditions (all P>0.1) indicated stability of arterial mechanical behaviour with repeat measurements. Comparing BPs obtained by standard inflation with those from standard deflation, manual SBP was 2.6 mmHg lower (P<0.01), manual DBP was 1.5 mmHg higher (P<0.01), manual PP was 4.2 mmHg lower (P<0.001), automated DBP was 6.7 mmHg higher (P<0.001) and automatic PP was 7.5 mmHg lower (P<0.001). There was no statistically significant difference for any automated BPs between fast and standard cuff inflation. The statistically significant BP differences between inflation and deflation suggest different arterial mechanical behaviour between arterial opening and closing during BP measurement. Conclusion We have shown that the mechanical behaviour of the brachial artery during BP measurement differs between cuff deflation and cuff inflation.