The 20th National Symposium on Mathematical Sciences was successfully held on December 18-20, 2012 in Putrajaya, Malaysia. This is the 20th symposium organized by the Malaysian Mathematical Sciences Society. This year, School of Mathematical Sciences, Universiti Kebangsaan Malaysia was honored to be the host of this symposium. The aim of this symposium is to bring together mathematicians and mathematical practitioners in Malaysia to promote collaboration and knowledge dissemination, new discoveries and innovations related to mathematical sciences. ... The symposium covers all topics in mathematical sciences, particularly pure mathematics, applied mathematics, engineering mathematics, mathematics educations, computational mathematics, mathematics and multimedia, statistics, optimization, operational research, actuarial science, finance and quality and productivity.