In an observational study of 31,257 children we investigated the effects of paternal age at the time of the child’s birth, paternal absence and non-biological fathers on children’s health. Results are per 5 year change in paternal age. Older fathers were associated with lower rates of unintentional injuries, odds ratio (OR)=0.966, P=0.0027. There was a quadratic association between paternal age and risk of hospital admission, beta=0.0121, P=0.0109, with minimum risk at paternal age 37.7. Absent fathers were associated with increased risk of hospital admission, OR=1.19, P<10(-3), lower rates of complete immunizations to 9 months, OR=0.562, P<10(-3), higher Strength and Difficulties Questionnaire (SDQ) difficulties scores: beta=0.304, P=0.0024 (3 year olds), beta=0.697, P<10(-3) (5 year olds). Non-biological fathers were associated with increased risk of unintentional injury, OR=1.16, P=0.0319 and hospital admission, OR=1.26, P=0.0166; lower rates of complete immunizations to 9 months, OR=0.343, P=0.0309 and higher SDQ difficulties scores: beta=0.908, P<10(-3).