Maternal alcohol or tobacco consumption may negatively impact the fetus and breastfeeding infants. Maternal tobacco consumption is also known to negatively affect exposed young children. The current study therefore aimed to assess the prevalence of these lifestyle behaviours in a sample of 6-24-months post-partum women and to elucidate socio-demographic and maternal factors associated with these behaviours. A community-based cross-sectional survey was conducted on 6-24-months post-partum women (n = 318) in three cities in the South Island of New Zealand. Self-reported data on current alcohol and tobacco consumption were collected from these women using a self-administered questionnaire. The results showed that nearly 72% and 23% of these women consumed alcohol and tobacco, respectively. Being Caucasian, having a higher level of education and higher household income were significant factors for alcohol consumption, while being of younger age and of lower educational status were significant factors for tobacco consumption. Pregnancy was associated with lower odds for alcohol consumption (0.07; P < 0.001), but not with lower odds for tobacco consumption. In contrast, breastfeeding was not associated with lower odds of alcohol consumption (0.08; P = 0.075). In conclusion, younger women with lower levels of education and household income must be targeted for public health education on the negative effects of tobacco consumption on their own health and on the health of their children.