Background: The World Health Organization recommends that mothers avoid early complementary feeding of infants before the age of 6 months, to promote maximum growth and health. However, this practice is still high among Saudi mothers. This study aimed to assess knowledge, attitude and practices (KAP) towards early complementary feeding among Saudi mothers in Riyadh. Methods: A crosssectional study was conducted in Riyadh city among 771 mothers of children, aged 6-24 months. Data was collected through an online questionnaire that assessed KAP aspect regarding early complementary feeding among mothers. Results: More than one-third of mothers (37.4%) had introduced early complementary feeding, out of which 83.3% later stated that the main reason for this was because they thought that the baby was old enough to receive complementary foods. The two most common types of complementary foods given to the baby before 6 months were liquids (83.0%) and mashed foods (72.9%). The mothers who introduced complementary feeding before 6 months of age compared to those who initiated complementary feeding after 6 months were observed to have a higher percentage of medium knowledge and neutral attitude (76.0% versus 54.4% and 55.2% versus 62.5%, (p<0.05), respectively). Mothers’ knowledge and attitude significantly influenced their practices in relation to early complementary feeding (p<0.05). Conclusion: The findings demonstrated that the appropriate knowledge and attitude are important to promote the introduction of complementary feeding at 6 months in the population that was studied. Thus, education on complementary feeding should be promoted.