Abstract: Five novel nor-eremophilane-type sesquiterpenoids, peniroqueforins E–H and J (1–4 and 7), two new eremophilane-type sesquiterpenoids, peniroqueforins I and K (5 and 8), and a new eudesmane-type sesquiterpenoid, peniroqueforin L (9), along with four known compounds (6 and 10–12), were isolated and characterized from fungus Penicillium roqueforti (P. roqueforti). The structures and absolute configurations of these compounds were determined through comprehensive spectroscopic analyses, electronic circular dichroism (ECD) data analyses, and single-crystal X-ray diffraction methods. The anti-multi-drug resistance (MDR) cancer activity of these compounds was evaluated using SW620/Ad300 cells. Notably, the half maximal inhibitory concentration (IC₅₀) value of paclitaxel (PTX) combined with 1 in SW620/Ad300 cells was 50.36 nmol·L⁻¹, which was 65-fold more potent than PTX alone (IC₅₀ 3.26 μmol·L⁻¹). Subsequent molecular docking studies revealed an affinity between compound 1 and P-glycoprotein (P-gp), suggesting that this nor-eremophilane-type sesquiterpenoid (1) could serve as a potential lead for MDR reversal in cancer cells through P-gp inhibition.