ABSTRACT: Medical professionals work in a constantly stressful environment. The nature of the profession requires routine extended working hours, but little is known about the effect of long working hours on selective physiological measures. A cross-sectional feasibility study was conducted from 1 October 2017 until 30 April 2018 on medical doctors in a tertiary health centre in northwest Malaysia. There was a total of 55 study participants recruited. The overall systolic blood pressure (SBP) was highest after working 24-hour stretch (p=0.006) and the overall diastolic blood pressure (DBP) were highest after working for 33 hours in a single stretch, at the end of on call rotation (p<0.001). Otherwise, there was no significant association between personality elements and fatigue scores. The study’s preliminary result demonstrated the potential harmful effects of long working hours on cardiac autonomic physiology and may serve as a potential projection to involve the residency options and recruitment via personality assessment among medical doctors.