In the current study, we examined the degree to which sudden gains (large, rapid, and stable symptom reduction in a one-session interval) predicted treatment outcome in adults randomized to two different trauma-focused treatments. Adults diagnosed with PTSD were randomized to either written exposure therapy (WET; n = 63), a brief, exposure-based treatment for posttraumatic stress disorder (PTSD), or the more time-intensive Cognitive Processing Therapy (CPT; n = 63). Findings showed that 20.6% of participants who received WET and 17.5% of participants who received CPT experienced sudden gains. Sudden gains occurred earlier in WET (M session = 2.69, SD = 0.75) than in CPT (M session = 5.64, SD = 3.01). However, there were no treatment condition differences in the magnitude of the sudden gains. Treatment outcomes were significantly better for those who experienced sudden gains compared with those who did not, regardless of treatment assignment. Exploratory analyses of participants' trauma narratives revealed that expressing more negative emotion predicted the occurrence of sudden gains in both treatment conditions. Negative beliefs about the self and others did not predict sudden gains. The findings are discussed in terms of how they may help identify individual early response patterns that predict outcomes in trauma-focused treatments.