Purpose: Childhood acute lymphoblastic leukemia (ALL) is the most common childhood malignancy and brain tumors (CBTs) are the leading cause of cancer death in children. In our Australian case-control studies of these cancers, we investigated whether parental alcohol consumption before or during pregnancy was associated with risk. Methods: Cases were identified through the ten Australian pediatric oncology centers, and controls were recruited through national random-digit dialling. Detailed information on alcohol consumption, including beverage type, amount, and timing, was collected from 690 case families (388 ALL and 302 CBT) and 1,396 control families. Data were analyzed using unconditional logistic regression. Results: We found no evidence that maternal alcohol use before or during pregnancy was associated with an increased risk of either cancer; rather, there was evidence of inverse associations, particularly with wine. For both cancers, we observed U-shaped associations with paternal alcohol consumption in the year before the pregnancy, possibly driven by reduced risk at moderate levels of beer and wine intake and increased risk associated with high levels of beer intake. Moderate intake of spirits by fathers was associated with an increased risk of CBT but not ALL. These findings would be strengthened by corroboration in other studies. While the inverse associations with wine may be interesting mechanistically, the public health message remains that maternal alcohol use during pregnancy causes serious disorders in the offspring and should be avoided. Conclusions: Our findings suggest that men, as well as women, should limit their alcohol intake when planning a pregnancy.