High measles incidence and frequent epidemics are reported in Pakistan, given the low coverage for measles vaccine. This study evaluated coverage of mass measles campaign 2011 and estimated parental awareness and determinants for low/no coverage. Household survey was conducted 4 months after the measles campaign in Karachi, Pakistan. Parents of children younger than 5 years were administered structured questionnaire about their knowledge and participation in measles campaign. Of 1020 eligible households, only 282 (28%) parents knew about measles supplementary immunization activity, mainly from public announcements (49%). Of these, 174 (62%) children received measles vaccine, whereas, 108 (38%) parents refused measles vaccine. Overall, only 17% children received measles vaccine during this campaign. Low maternal education, not having received DPT/Pentavalent-3 vaccine, and routine vaccination from public Expanded Program on Immunization facility were significant determinants for low coverage. Measles vaccine coverage in Karachi remains low, and sporadic outbreaks of measles every 2 to 3 years are expected unless population coverage can be rapidly increased.