Abstract: Mixed oxides catalyst has become a recent focus for production of biodiesel from the third-generation biomass. In this study, ZrO2 was synthesized by using sol�gel method with hydrothermal assisted. Mixed oxides catalysts were then prepared via incipient wetness impregnation of Bi2O3 (5, 15 and 30 wt) on the synthesized ZrO2. Physicochemical properties of the catalysts were evaluated using different characterization techniques and their performances were investigated in the transesterification of marine microalgae of Nannochloropsis oculata to biodiesel. XRD diffractograms showed the presence of monoclinic (m) and tetragonal (t) phases of ZrO2 in all synthesized catalysts. It was found that the composition of the ZrO2 phases depend strongly on the Bi2O3 content. BET analyses showed that the total surface area of ZrO2 decreased with increased Bi2O3 content due to the pore filling effect. CO2-TPD and NH3-TPD analyses indicated that all the catalysts possessed both acidic and basic properties with different intensities. The highest FAME yield was obtained using 5Bi2O3/ZrO2 when the test was conducted at optimum reaction conditions of 20 wt of catalyst loading and methanol to biomass ratio of 90:1 (mL/g) at 80 °C for 6 h. The synthesized biodiesel met the specifications of biodiesel standard for cetane number and iodine value except for the oxidative stability. Graphical Abstract: Figure not available: see fulltext. © 2019, Springer Nature B.V.