The crystallization of molecular sieve ZSM-12 has been investigated by employing benzyltrimethylammonium chloride (BTMACl), tetraethylammonium bromide (TEABr) and methyltriethylammonium bromide (MTEABr) as templates. The crystallization of pure ZSM-12 framework was accomplished at Si/Al ratio of 90. The pure ZSM-12 samples so obtained were judged with respect to the differences in X-ray diffraction patterns, morphology, crystal size and total acidity to understand the role of template during crystallization. Interestingly, crystallization of ZSM-12 phase with rice, cubic and elongated cubic shaped morphology was favored in the presence of BTMACl, TEABr, and MTEABr, respectively. Finally, the effect of zeolite crystal size and morphology on hydroisomerization reaction was investigated by employing ZSM-12 (Si/Al = 90) based hydroisomerization catalysts. The performance of the prepared catalysts was judged in terms of their activity, selectivity and product distribution for the hydroisomerization reaction using n-hexadecane as a model feed. Based on the obtained results, the possible advantages of using a ZSM-12 sample of specific morphological features and crystal size for hydroisomerization of long chain n-paraffins are discussed. © 2013 Elsevier Inc. All rights reserved.