•We investigated factors associated with vaccination of healthy, young children.•Perceived adverse effects of the vaccine and positive attitudes to vaccines are important.•Mixed evidence for perceived susceptibility to, and perceived severity of illness.•Understanding these factors can help inform future communication about vaccines. Many parents make a conscious decision not to vaccinate their child. Multiple beliefs and perceptions surround this choice. If uptake of routine child vaccination is to increase, public health communications about vaccines must be informed by evidence on the factors affecting uptake. We conducted a systematic review to investigate psychological, social and contextual factors associated with uptake of routine vaccines in young children. Studies were included if they reported analyses of the association between psychological factors and uptake or included parents’ self-reported reasons for or against vaccination. Our search identified 9110 citations after deduplication. Sixty-eight citations describing sixty-four studies were included in the review. The quality of the studies was mixed. There is strong evidence for an association between vaccination uptake and: not perceiving vaccines to cause adverse effects; general positive attitudes towards vaccination; positive vaccine recommendations; and perceiving fewer practical difficulties of vaccination. While there was good evidence for an association between vaccination and perceived susceptibility to the illness, evidence for an association between perceived severity of an illness and vaccination was weak. Other factors associated with vaccination include knowledge about the vaccine, social influences and trust in the healthcare profession. Having increased information about the vaccine was associated with vaccination, but the influence of different sources of information needs more research. Understanding which factors are consistently associated with the decision to vaccinate one’s child is important to identify messages which should be targeted by public health communications about routine child vaccinations.