Herein, we have fabricated microcellular injection-molded foams by combining long-chain branched polypropylene (LCBPP) and 1,3:2,4 bis-O-(4-methylbenzylidene)-D-sorbitol gelling agent (MD) using a core-back foam injection molding (FIM) technique. Microcellular foams of LCBPP/MD blends having an average cell diameter of approximately 2.5 mu m and a cell density on the order of 10(10) cells/cm(3) were achieved with a void fraction of 50%. Fast scanning chip calorimetry results revealed that the added MD acted as effective nucleating agents and promoted crystallization for the LCBPP. Interestingly, the development of microcellular foams led to notable advances in tensile toughness from 44.1 MJ/m(3)/(g.cm(-3)) and 111% of neat LCBPP foams to 172.1 MJ/m(3)/(g.cm(-3)) and 440% of LCBPP/MD blend foams in terms of specific breaking energy and elongation at break, respectively. These results revealed that the lightweight microcellular PP with improved toughness could be developed using FIM, which offers a viable approach to fabricate injection-molded products for large-scale applications. (C) 2017 Elsevier Ltd. All rights reserved.