There is limited information on sleep patterns among infants and toddlers in Spain. The aim of this study was to assess sleep patterns in children three to 36 months of age in Spain. A cross-sectional study was conducted between February 2017 and February 2018. Sociodemographic data and sleep variables were collected using an expanded version of the validated Spanish version of the brief infant sleep questionnaire. A total of 1,404 parental reports on children (725 males; 679 females) with a mean age of 18.8 ± 9.5 months were collected. Parents who perceived their child's sleep as problematic (39% of our sample) reported fewer sleep hours (median 9 versus 10 h), more night awakenings (median 2 versus 1), and longer periods of nocturnal awakenings (median 0.5 versus 0.08 min) (p < 0.001). Parental presence at the time of sleep onset and later and irregular bedtime routines were significantly associated with a reduction in total sleep time, longer sleep latency, and disruptive night awakenings (p < 0.001). These findings highlight the need for further studies to assess how to improve sleep patterns as a relevant modifiable lifestyle factor.Conclusion: A substantial percentage of the population perceived that their children slept poorly, which was evident in a variety of sleep patterns, including sleep duration and sleep quality. What is known: • Previous research has established that sleep difficulties among pediatric population affect up to 30% of all children and up to 20-30% of infants and toddlers. • A positive relationship between less parental bedtime involvement and sleep consolidation in infants and toddlers has been established. What is new: • More than a third of Spanish parents perceived their infants and toddlers sleep as problematic and their children reportedly have shorter night sleep hours, more night awakenings, and longer periods of nocturnal awakenings. • Later and irregular parental bedtime routines were associated with worst infants and toddlers sleep.