Background: Patients with locally advanced pancreatic cancer have a dismal prognosis, with a median overall survival (OS) of 12–14 months with systemic therapies. Irreversible electroporation (IRE), a nonthermal ablative technique, may prolong survival of patients with locally advanced pancreatic cancer. Purpose: To investigate the safety and efficacy of percutaneous IRE for locally advanced pancreatic cancer and locally recurring pancreatic cancer in a prospective phase II trial. Materials and Methods: Between December 2012 and September 2017, participants with locally advanced pancreatic cancer or postresection local recurrence were prospectively treated with percutaneous CT-guided IRE (ClinicalTrials.gov identifier: NCT01939665). The primary end point was median OS from diagnosis. The target median OS was 11.6 months for participants receiving no induction chemotherapy or gemcitabine-based induction chemotherapy and 14.9 months for those receiving induction 5-fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX). Results: Fifty participants (25 men and 25 women; median age, 61 years [interquartile range, 56–69 years]; 40 with locally advanced pancreatic cancer and 10 with local recurrence) were included. Median OS measured by using the Kaplan-Meier method was 17 months from diagnosis of locally advanced pancreatic cancer (95% confidence interval [CI]: 15 months, 19 months) and 10 months from IRE (95% CI: 8 months, 11 months). In the locally advanced pancreatic cancer group, 18 participants received no therapy or gemcitabine-based induction chemotherapy and 22 received FOLFIRINOX. The median OS from diagnosis was 17 months for both groups (95% CI: 7 months, 28 months and 15 months, 18 months, respectively; P = .26). For participants with postresection local recurrence, the median OS was 16 months from diagnosis of recurrence (95% CI: 11 months, 22 months) and 9 months from IRE (95% CI: 2 months, 16 months). After IRE, local recurrence developed in 23 of the 50 participants (46%). Tumor volume of 37 cm 3 or greater (hazard ratio [HR], 2.9; P = .02), pre-IRE carbohydrate antigen 19-9 (CA 19-9) level of 2000 U/mL or greater (HR, 12.1; P = .001), and decrease in CA 19-9 level of 50% or less 3 months after IRE (HR, 3.1; P = .01) were predictors of worse survival. Fourteen minor and 21 major complications occurred in 29 of the 50 participants (58%). Two participants died less than 90 days after IRE; one of these deaths was likely related to IRE. Conclusion: The target median overall survival with CT-guided percutaneous irreversible electroporation was exceeded in participants with locally advanced pancreatic cancer (17 months) and those with local recurrence (16 months).