Sleep problems are common during infancy. Possible factors which contribute to parental perception of problem sleep were investigated as part of a pilot study collecting objective data on the sleep of 1-year-old New Zealand infants (n= 52 families). Sleep of each infant was monitored for a week at home (ankle actigraphy and sleep diaries, which also included daily infant mood ratings) and parents completed questionnaires addressing their infant's sleep, the living and sleeping environment, and feeding. Thirty-five percent of the infants were considered by parents to have a sleeping problem. These infants had shorter night-time sleep as measured by actigraphy (median = 10.0 h vs 10.7 h for non-problem sleepers [U= 193.0, P < 0.05]), less total sleep per 24 h (median = 11.4 h vs 12.5 h [U= 169.5, P < 0.01]), and were put to bed more often per 24 h (median = 3.5 times vs 3.0 times [U= 201.5, P < 0.05]). Problem sleepers were also more likely to spend ≥ 20 min awake at night (68% vs 32% [χ2= 16.78, P < 0.001]), as well as currently being breastfed (55% vs 45% [χ2= 5.97, P < 0.05]), and to have moderate–bad mood at bedtime (59% vs 41% [χ2= 6.54, P < 0.05]). Sleep was also related to parent's diary ratings of their infant's mood and temperament. This study highlights factors contributing to parental perception of problem sleep which is vital for recognizing and managing such problems throughout infancy.