Background: Liposomal irinotecan (nal-IRI) plus fluorouracil/leucovorin (5-FU/LV) has demonstrated its clinical benefit in patients with metastatic pancreatic adenocarcinoma (mPAC) who progressed on prior gemcitabine-based chemotherapy. However, its role in patients who previously treated with conventional irinotecan has not been investigated. We analyzed clinical outcomes of nal-IRI + 5-FU/LV in mPAC patients after progression on conventional irinotecan-containing chemotherapy. Methods: In this multicenter retrospective analysis, a total of 35 patients with mPAC who received nal-IRI + 5-FU/LV after progression on irinotecan-containing regimen, between January 2017 and March 2020, were included. The ratio of time-to-progression (TTP) with nal-IRI + 5-FU/LV to TTP with conventional irinotecan (TTPr) was correlated with duration and cumulative dose of prior conventional irinotecan. Results: The median age was 58 years (range, 35-73) and 16 patients (46%) were male. All patients received prior irinotecan as the component of FOLFIRINOX. The median duration of prior irinotecan was 4.6 months (range, 0.5-16.8) and median cumulative dose of prior irinotecan was 1230 mg (range, 150-4650). Objective response rate of nal-IRI + 5-FU/LV was 2.9% (1 partial response) and stable disease was achieved in 31.4% (n = 11). With median follow-up duration of 9.2 months [95% CI, 7.8-10.5], the median PFS and OS were 2.0 months [95% CI, 1.4-2.6] and 4.4 months [95% CI, 3.6-5.7], respectively. 6-month PFS rate was 16.3% and OS rate was 37.5%. The median TTPr was 0.41 (range 0.07-2.07) and this showed negative correlation between cumulative dose of prior irinotecan (R = -0.37, p = 0.041). There was a tendency for the negative correlation between TTPr and duration of prior irinotecan (R = -0.35, p = 0.062). Most common grade 3-4 toxicities were neutropenia (20%) and fatigue (8.6%). Conclusions: Nal-IRI + 5-FU/LV showed only modest efficacy for mPAC patients who progressed on conventional irinotecan-containing chemotherapy. Cumulative dose of prior conventional irinotecan may be correlated with the efficacy of nal-IRI + 5-FU/LV.