Early attention bias to threat-related negative emotions may lead children to overestimate dangers in social situations. This study examined its emergence and how it might develop in tandem with a known predictor namely temperamental shyness for toddlers' fear of strangers in 168 Chinese toddlers. Measurable individual differences in such attention bias to fearful faces were found and remained stable from age 12 to 18 months. When shown photos of paired happy versus fearful or happy versus angry faces, toddlers initially gazed more and had longer initial fixation and total fixation at fearful faces compared with happy faces consistently. However, they initially gazed more at happy faces compared with angry faces consistently and had a longer total fixation at angry faces only at 18 months. Stranger anxiety at 12 months predicted attention bias to fearful faces at 18 months. Temperamentally shyer 12-month-olds went on to show stronger attention bias to fearful faces at 18 months, and their fear of strangers also increased more from 12 to 18 months. Together with prior research suggesting attention bias to angry or fearful faces foretelling social anxiety, the present findings point to likely positive feedback loops among attention bias to fearful faces, temperamental shyness, and stranger anxiety in early childhood.