Objective: To explore the use of rapid needs assessment (RNA) surveys to determine the prevalence and factors contributing to delays in vaccination of children in two low middle-income countries (LMIC). Methods: Data from two RNA surveys performed as part of program improvement evaluations in Guatemala and Peru were used for this analysis. The primary endpoint was the timeliness of immunization with delay defined as administration of vaccines beyond 28 days from recommended age for DTwP-HepB-Hib (Penta) and measles mumps rubella (MMR) vaccines, as well as past age-restrictions for rotavirus vaccine. Independent risk factors analyzed included child's gender, birth year, number of children in household, maternal age, maternal education, and food insecurity. Results: Vaccine information was available from 811 children from 838 households surveyed. High rate of immunization delays was observed, with 75.6% of children in Guatemala and 57.8% of children in Peru being delayed for the third dose of Penta primary series. Factors associated with delayed vaccination in Guatemala included advanced maternal age and increased number of children in household. In Peru, significant associations were birth year before 2009, lower maternal education level, and increased number of children in household. Conclusions: RNA is a fast and effective method to identify timely vaccine coverage and derive a hypothesis of factors possibly associated with vaccination delay.