Objective: To explore demographic and social support predictors of health-related quality of life (HRQoL) (mental and physical) for childbearing women in the perinatal period. Design: Longitudinal. Sample: Three public hospitals in metropolitan Brisbane, Australia. Participants: Four hundred seventy-three (473) women recruited at 36 weeks of pregnancy, and 6 and 12 weeks following childbirth. Methods: The Short Form-12 (SF-12) Version 2 Health Survey was used to measure the mental and physical domains of HRQoL. Social support was measured using the Maternal Social Support Scale (MSSS). Results: Mean scores for the mental and physical domains of HRQoL were lower than population norms. Social support was found to be a significant and consistent predictor of higher HRQoL scores, particularly in the physical domain at 12 weeks following child birth and mental domain during the perinatal period. The relationship between social support and HRQoL was found to be independent of other factors including education, length of relationship with partner, age, parity, and antenatal visit. The only other significant predictor was length of relationship with partner in the mental domain at 36 weeks of pregnancy. Conclusion: Social support is a significant and consistent predictor of a mother's HRQoL during the perinatal period. Nurses and midwives need to assess social support, rather than making assumptions based on demographic factors.