This randomized controlled trial (NTR5697) examined the effects of a 5-week daily skin-to-skin contact (SSC) intervention, compared with care-as-usual, on full-term infant crying and sleeping duration during the first 12 weeks postnatally (secondary outcomes of this trial). This trial included 116 Dutch healthy mothers and their full-term infants. SSC mothers were instructed to provide 1 hr daily of SSC for the first 5 weeks postpartum. Intention-to-treat analyses revealed no group differences in infant crying (i.e., total duration and mean bout length) and sleeping (i.e., total duration and mean bout length). Per-protocol analyses, including only the SSC dyads who adhered to SSC guidelines, indicated that SSC reduced infant total crying duration and the crying bout length. Similarly, dose-response analyses indicated that more SSC minutes were associated with less infant crying (i.e., shorter total duration and bout length) and longer total sleeping duration, especially when the infant was younger. No group differences and associations were found with sleeping bout length. Mother-infant SSC, when performed regularly, may be a cost-effective intervention to reduce infant crying and potentially also extend infant sleep duration.