Postoperative physiotherapy has been shown to reduce the incidence of postoperative pulmonary complications after open abdominal surgery. This study aimed to determine if the addition of deep breathing exercises and secretion clearing techniques to a standardised physiotherapist-directed program of early mobilisation improved clinical outcomes in patients undergoing open abdominal surgery. Fifty-six patients undergoing open abdominal surgery, at high risk of developing postoperative pulmonary complications, were randomised before operation to an early mobilisation-only group or an early mobilisation-plus-deep breathing and coughing group. Mobility duration, frequency and intensity of breathing interventions were quantified for both groups. All outcomes were assessed by a blinded outcomes researcher using a standardised outcomes measurement tool developed specifically for this population. Outcomes included incidence of clinically significant postoperative pulmonary complications, fever, length of stay, and restoration of mobility. There were no significant differences between groups in mean age, anaesthetic time, perioperative morbidity, or postoperative mobility. Outcome data were available for 89% of enrolled subjects. Overall incidence of postoperative pulmonary complications was 16%. The incidence of postoperative pulmonary complications in the non-deep breathing and coughing group was 14%, and the incidence of postoperative pulmonary complications in the deep breathing and coughing group was 17%, (absolute risk reduction -3%, 95% C1 -22 to 19%). There was no significant difference between groups in the incidence of fever, physiotherapist time, or the number of treatments. This study suggests that, in this clinical setting, the addition of deep breathing and coughing exercises to a physiotherapist-directed program of early mobilisation does not significantly reduce the incidence of clinically significant postoperative pulmonary complications in high risk open abdominal surgery subjects.