Background Increased psychophysiological reactivity is a hallmark intermediate phenotype of posttraumatic stress disorder (PTSD). Individuals with PTSD exhibit greater skin conductance (SC) responses to trauma scripts than trauma survivors without PTSD. However, trauma scripts require time for development and cannot be easily used in a single visit. Thus, there is a need for a low‐cost, easy‐to‐use, SC recording protocol for PTSD assessment. Methods Using a mobile device (eSense) connected to a portable tablet computer, we assessed SC reactivity to a standard trauma interview (STI) in 63 participants recruited from Grady Memorial Hospital in Atlanta, GA, approximately 1 year after trauma exposure. SC response (SCR) was calculated by subtracting the SC level (SCL) at the end of the baseline recording from the maximum SCL during the STI. Results SCL was significantly higher during the STI compared to baseline (P < .001), and individuals with PTSD showed significantly greater SCR than individuals without PTSD (P = .006). Logistic regression using SCR with PTSD diagnosis as the outcome showed an odds ratio of 1.76 (95% CI: 1.11–2.78). Lastly, higher SCR during the STI was also significantly associated with PTSD symptom total score controlling for demographics and trauma severity (b = 0.42, P = .001). Conclusions The current study demonstrated feasibility of the use of a mobile device for assessing psychophysiological reactivity in those with PTSD. The use of this low‐cost, easy‐to‐use mobile device to collect objective physiological data in concert with a STI can be easily disseminated in clinical and research settings.