On May 3, 2016, mandatory evacuation order was declared for Fort McMurray region as wildfire threatened. Over 90,000 residents were evacuated and firefighters from Canada and abroad worked constantly to protect the municipality. Overall, fire consumed about 2400 homes and over 200,000 ha of forest, reaching into Saskatchewan. The evacuation order was lifted with residents returning to the Municipality in phases from June 1, 2016. The aim of this study is to assess likely prevalence of PTSD in residents of Fort McMurray 6 months after a wildfire and to determine the predictors of likely PTSD in the respondents. A quantitative cross-sectional survey was used to collect data through self-administered paper-based questionnaires to determine likely PTSD. The PTSD Checklist for DSM 5 Part 3 was used to assess the presence or absence of likely PTSD in respondents randomly selected from a variety of natural settings in Fort McMurray. Data were analyzed with SPSS version 20 using univariate analysis with the chi-squared test and binary logistic regression analysis. One-month prevalence rate among adult residents for likely PTSD 6 months after the disaster was 12.8% (14.9% for females and 8.7% for males). While controlling for other factors in the logistic regression model, corresponding odds ratios included 9.51 and 4.88 for those who received no or only limited support respectively from friends/family, 8.00 for those who had history of an anxiety disorder before the wildfire, and 4.01 for those who received counseling after the wildfire. Respondents who presented with likely PTSD were significantly more likely to self-report increased drug abuse, but not increased alcohol use, after the fire. Our study has established that while support from family/friends following wildfires may be protective against likely PTSD, a prior diagnosis of an anxiety disorder significantly increased risk for developing PTSD. Further studies are needed to explore whether receiving counseling after a wild fire alters the likelihood of individuals presenting with PTSD.