The synergistic effect between metal and acid sites has been considered to be of great importance to n-alkane hydroisomerization catalyzed by bifunctional catalysts. Herein, we report a facile mercaptosilane-assisted in situ synthesis approach to achieve stable and highly dispersed small Pt nanoparticles supported on HL zeolite catalysts (Pt/HL-SH) for n-hexane hydroisomerization. In comparison with the catalysts (Pt/HL-C) synthesized by a traditional ion-exchange method, the Pt/HL-SH catalysts show both high activity and excellent catalytic stability and also no obvious sintering of Pt nanoparticles is observed during the reaction due to the fact that the Pt/HL-SH catalysts possess both higher dispersion of Pt particles within the HL nanocrystals and more mesopores produced by mercaptosilane. Moreover, the regeneration stability of n-hexane hydroisomerization over Pt/HL-SH catalysts was also examined by five continuous cycles, demonstrating excellent regeneration properties. Thus, the mercaptosilane-assisted in situ synthesis approach is a promising way to prepare bifunctional catalysts for enhancing their catalytic performance in n-alkane hydroisomerization.