Abstract A randomised, open-label study compared the immunogenicity and safety of 7-valent pneumococcal conjugate vaccine (PCV7) and meningococcal C conjugate vaccine (MnCC vaccine) administered concomitantly and individually. Infants received PCV7 + MnCC vaccine ( n = 265), PCV7 alone ( n = 268) or MnCC vaccine alone ( n = 178). PCV7 was administered at 2, 3½, 6 and 12 months, and MnCC vaccine at 2, 6 and 12 months. For the 7 pneumococcal serotypes tested (4, 6B, 9V, 14, 18C, 19F and 23F), proportions of subjects with pneumococcal serotype-specific immunoglobulin G (IgG) antibody concentrations ≥0.35 μg/mL post-infant series were non-inferior for the PCV7 + MnCC vaccine (91.5–99.6%) and PCV7 (89.0–99.6%) groups. Proportions of subjects achieving serogroup C meningococcal serum bactericidal assay titres ≥1:8 post-infant series were non-inferior for the PCV7 + MnCC vaccine (99.6%) and MnCC vaccine groups (98.8%). Pneumococcal IgG antibody levels were similar in the PCV7 + MnCC vaccine and PCV7 groups at each time point. Post-infant and post-toddler meningococcus C serum bactericidal assay titres and IgG levels were similar in the PCV7 + MnCC vaccine and MnCC groups, although pre-toddler, the levels were lower in the PCV7 + MnCC vaccine group than the MnCC vaccine group. Immune response rates to diphtheria antigen approached 100% for all vaccine groups. Local reactions were mostly similar among the treatment groups. The MnCC vaccine group had lower rates of some systemic events than the PCV7 + MnCC vaccine group. Immune responses to PCV7 + MnCC vaccine were non-inferior compared with those seen with each vaccine administered alone.