Background: To determine the frequency of HER-2 overexpression in colorectal cancer (CRC) patients, and to explore the relationship between clinicopathological prognostic factors and their effects on survival, based on immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH) analysis. Materials and Methods: The study included 80 patients with a histologically proven diagnosis of CRC that received adjuvant FOLFOX-4 chemotherapy at our department between March 2006 and September 2010. Patient data were analyzed retrospectively. Results: The median follow-up period and age of the patients were 24 months and 59 years, respectively. In immunohistochemical staining, 3+ staining was found in 2 patients (2.5%) while 2+ was in 13 (16%). FISH for HER-2 was performed for all of these 15 patients; samples which were 3+ showed positivity but the ones with 2+ were negative. There was no significant correlation between HER-2 expression and age, gender, tumor localization, histological subtype, grade, lymphovascular and perineural invasion, or pTN stage (P>0.05), even when the patients with HER-2 overexpression were analyzed separately. There was also no significant relationship between progression-free survival (PFS) and overall survival (OS), and HER-2 expression, gender, tumor localization, obstruction-perforation, bleeding, histological type, grade, lymphovascular and perineural invasion, or pT staging (P>0.05); however, there was a significant relationship between lymph node involvement, and PFS and OS (P<0.05). Conclusions: Evaluation of HER-2 overexpression in a more comprehensive, multi-center, prospective trial with standardized methods will be an appropriate approach.