Urban families in middle-income countries are currently facing cultural and lifestyle transition. Changing from an agricultural to an industrial society may affect family roles and child-care practices. The present study aims to reveal family attitudes, knowledge and practices focusing on complementary feeding (CF). A cross-sectional study was conducted in three Child Health Clinics in Chiang Mai, Thailand. Self-administered questionnaires were given to families caring for healthy infants and children less than 18 months of age during October to November 2016. One-hundred and eight respondents completed questionnaires. The study found different attitudes and knowledge gaps between the respondents who were mothers and other family members ('others'). The 'others' were less likely to value CF as a crucial factor promoting child growth and development. Moreover, they had misperceptions about the benefits of animal-based protein and were less confident in their ability to feed the child properly. Most families reported timely introduction of complementary food, using proper milk products and encouraging age-appropriate feeding methods. However, there were undesirable practices including delaying introduction of animal-based protein, inadequate food diversity, the use of seasoning, feeding premasticated food and offering food as a reward. These findings suggest that nutritional education should be extended to all caregivers involved in CF to improve the adherence to feeding recommendations.