Inclusion Criteria:  (i) Male or female 18-65 years old;  (ii) Individuals who are either:  Employed full-time as part of the Canadian or US military forces or the RCMP; On leave of absence from Canadian or US military forces, or the RCMP; Veterans of the Canadian or US military forces or the RCMP;  (iii) Evidence of a personally signed and dated informed consent form;  (iv) Individuals suffering from occupationally related PTSD, as defined by the DSM-5, for 6 consecutive months or more.  (v) Females of childbearing potential willing to use contraception for the duration of the treatment period of the study.  Exclusion Criteria:  (i) Basal systolic blood pressure < 100 mm Hg;  (ii) Basal heart rate < 50 BPM;  (iii) Medical conditions contraindicating the administration of propranolol or beta blockers  (iv) A known hypersensitivity to propranolol or any of the study product or placebo ingredients;  (v) Clinically significant lactose intolerance;  (vi) Use of medication that involves unwanted interactions with propranolol including but not limited to other beta-blockers, anti-arrhythmic medications, and calcium channel blockers;  (vii) Current use of propranolol;  (viii) Pregnant or breast-feeding women;  (ix) Individuals with borderline personality, bipolar disorder, psychosis;  (x) Current DSM-5 substance dependence;  (xi) Active suicidal ideations, as demonstrated by a response of 2 or 3 on item 7 of the Beck Depression Inventory - Short Form;  (xii) A score below 'moderately ill' on the severity scale of the Clinical Global Impression scale;  (xiii) Participating in active litigation related to the traumatic event (Veterans Affairs Canada claims are permitted, excluding judicial claims);  (xiv) Strong dissociative tendencies, as evidenced by the Dissociative Experience Scale (8-item version, DES-T);  (xv) Suspected or confirmed traumatic brain injury during the last 24 months;  (xvi) Understanding neither English nor French;  (xvii) Participants who receive exposure-based cognitive-behavioral therapy during the treatment phase of the study;  (xviii) Presence of any medical condition that in the opinion of the investigator may compromise patient safety or study objectives.