Background: Therapy options for second-line treatment of advanced pancreatic adenocarcinoma (PDAC) are limited and preferred regimens have not been established. This study compared the efficacy and safety of modified FOLFIRINOX (mFFX) and sequential chemotherapy (FOLFIRI/FOLFOX) as second-line treatment for advanced PDAC. Methods: This was a retrospective single-center analysis of all patients who received mFFX or sequential chemotherapy between December 2014 and May 2019 as second-line treatment for advanced PDAC. The sequential arm included all patients intended to be treated with sequential chemotherapy even if finished with either FOLFIRI or FOLFOX. For efficacy analysis, progression-free survival (PFS), overall survival (OS), and response rate (RR)of all the patients, excluding those with locally advanced pancreatic cancer (LAPC), were evaluated. For safety analysis, we evaluated the incidence of grade ≥3 adverse events in all the patients. Results: Seventy-four patients (mFFX 44; sequential 30) were included.The patients characteristics (mFFX/sequential) are as follows:median age 64/67 years, performance status (ECOG) 0 50%/53%, and LAPC 16%/13%. In contrast to sequential therapy, the mFFX group showed better OS and RR. However, there was no significant difference between mFFX and sequential therapy in PFS (median 4.4 [95% confidence interval (CI) 1.8-7.9] vs. 4.6 [95% CI 2.0-6.2] months; hazard ratio [HR] 0.88 [95% CI 0.51-1.56]; p = 0.657), OS (median 10.6 [95% CI 5.9-13.8] vs. 8.5 [95% CI 5.0-12.2] months; HR 0.71 [95% CI 0.37-1.41]; p = 0.318), and RR (8.1% vs. 3.8%; odds ratio 1.94 [95% CI 0.19-19.87]; p = 1.000). In the safety analysis, grade ≥3 rates of neutropenia, febrile neutropenia, and anorexia were 36.4%, 6.8%, and 16.0%, respectively, with mFFX and 0%, 0% and 3.3%, respectively, with sequential chemotherapy. Conclusions: Whereas certain trends were observed, there were no significant differences in efficacy between mFFX and sequential chemotherapy. Considering the incidence of grade ≥3 adverse events with mFFX, sequential chemotherapy could be considered as one of the second-line treatment options for advanced PDAC.