© The Author 2016. Published by Oxford University Press. All rights reserved. Although the habits of cigarette smoking and associated coffee drinking are generally ceased during pregnancy, they are often reinitiated after delivery when the breastfeeding period starts. This is a case report of a 32-year-old lactating smoker mother who consumed caffeinated drinks and who agreed to donate breast milk after smoking one cigarette (containing 0.6 mg of nicotine) and drinking one cup of espresso (containing 80 mg of caffeine) for an investigation of the excretion of nicotine, its major metabolite cotinine and caffeine into the breast milk and subsequent transfer to the infant. Nicotine and its metabolite cotinine peaked in the breast milk at 0.5 h after the cigarette smoking, and caffeine peaked 2 h after drinking coffee. Moreover, the nicotine disappeared from the milk by 3 h, the caffeine required 24 h and the cotinine required 72 h. The relative infant doses of caffeine, nicotine and cotinine were found to be 8.9, 12.8 and 77.6%, respectively. In the light of these results obtained after the mother smoked only one cigarette and consumed one cup of espresso, if a lactating mother cannot refrain from smoking cigarettes, she should extend the time between the last smoked cigarette and breastfeeding to at least 3 h when the nicotine has been completely eliminated from the milk. Similarly, nursing mothers should also drink coffee sparingly and immediately after nursing and avoid coffee or caffeinated beverages for at least 4 h prior to breastfeeding to minimize the infant's exposure to caffeine.