Sixty-three patients with displaced humerus shaft fractures less than 2 weeks old requiring surgery were randomized to undergo locking plate fixation (LCP; n=33) or interlocking nail (ILN; n=30) fixation. The outcomes of interest included function evaluated using the American Shoulder and Elbow Surgeons (ASES) and the University of California at Los Angeles (UCLA) shoulder scores, the Short Form-36 (SF-36) questionnaire, and the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, pain on a visual analogue scale (VAS), and incidence of complications (i.e. iatrogenic radial injury, re-operation for nonunion, superficial infection, and deep infection). As well, time to fracture union, length of hospital stay, and time of operation were also recorded. Outcomes were measured at the time of first callus observation, and again at 24 months post-surgery. Sub-group analysis were conducted according to fracture type, specifically AO classification type A, and AO types B and C. Results demonstrated that VAS pain (p=0.017) and UCLA scores (p=0.034) for function were statistically significantly in favour of the LCP group vs ILN group at 24 months post-operation. Moreover, no cases of deep infection was observed in any of the groups and no statistical significant differences was recorded between the 2 groups with respect to incidence of complications (p>0.05). In the subgroup analysis of AO Type A fractures, DASH score was statistically significantly in favour of the LCP group at first callus observation (p=0.029), but this difference was not observed at 24-months follow-up. Moreover, when comparing LCP AO Type A fracture vs ILN Types B and C fracture, VAS pain was statistically significantly improved in favour of the LCP AO Type A at 24-months follow-up (p=0.037). Comparing LCP AO Types B and C fractures to ILN AO Type A fractures, ASES scores were statistically significantly improved at first callus observation (p=0.027) in the LCP AO Types B and C group; all other outcomes were not statistically significantly different between the 2 groups (p>0.05). The length of surgical time was statistically significantly longer in the LCP group (p=0.001). The LCP group had a statistically significantly shorter hospital stay compared to the ILN group (p=0.043).