The highest incidence of invasive meningococcal disease is in young children, with a second peak in adolescents/young adults. All five major disease-causing serogroups (A, B, C, W-135 and Y) have been described in Asia. Immunogenicity and safety of the investigational meningococcal ACWY-tetanus toxoid conjugate vaccine (ACWY-TT, GlaxoSmithKline Biologicals) was evaluated in healthy, meningococcal conjugate vaccine-naïve adolescents in the Philippines, India and Taiwan. 1025 adolescents were randomized (3:1) to receive one dose of ACWY-TT or tetravalent ACWY polysaccharide vaccine (Mencevax™, Men-PS). Serum bactericidal activity using rabbit complement (rSBA) was measured. Local and systemic adverse reactions were recorded for 4 days. Safety data were pooled with results from a second, similarly designed study in adults for evaluation of grade 3 systemic events. The pre-specified immunogenicity criterion for non-inferiority to Men-PS was met. One month post-vaccination, ≥85.4%-97.1% had a vaccine response (post-titre ≥1:8 in initially seronegative and ≥4-fold increase in seropositive), versus 78.0%-96.6% after Men-PS, against each vaccine serogroup. Exploratory comparisons showed statistically significantly higher post-vaccination rSBA geometric mean titres against all serogroups following ACWY-TT versus Men-PS. Exploratory analysis showed no statistically significant differences between groups in grade 3 general symptoms; however, the statistical criterion for non-inferiority between pooled treatment groups in terms of the ratio of incidences of grade 3 general symptoms was not demonstrated. No SAEs were related to vaccination. ACWY-TT was immunogenic in Asian adolescents with a reactogenicity profile that was clinically acceptable and similar to that of licensed Men-PS. The results of this study indicate that ACWY-TT could be used as a third conjugate vaccine in the protection of adolescents against meningococcal disease.