The objective of this study was to determine the effect of stage of lactation on the concentration of polyamines (spermine, spermidine, and putrescine) in sow colostrum and milk. Ten, third parity sows (Landrace×Yorkshire) were sampled throughout a 28-day lactation. Litter size for all sows was standardized at 10 sucking piglets immediately after farrowing. Colostrum collection began at the birth of the first piglet (0 h), and colostrum was subsequently collected 6, 12, 18, and 24 h after farrowing. Sow milk was sampled on days 3, 7, 10, 14, 17, 21, 24 and 28 of lactation. Spermine concentration in sow colostrum was relatively constant for the first 12 h after farrowing and then rapidly increased to 10·26 μmol/l 24 h after farrowing (linear and quadratic effect; P<0·01). In contrast, the concentrations of spermidine and putrescine showed little change during the first 24 h with spermidine concentration in colostrum ranging from 3·76 to 4·54 μmol/l, and putrescine concentration ranging from 1·15 to 1·52 μmol/l. The highest concentration of spermine in sow milk was 18·82 μmol/l, observed on day 7, with levels gradually declining to 4·28 μmol/l by day 28 of lactation (linear and quadratic effect; P<0·01). In contrast, the concentration of spermidine increased during lactation ranging from a low of 4·32 μmol/l on day 7 to a high of 9·01 μmol/l on day 28 of lactation (linear effect P<0·01; quadratic effect P=0·03). Putrescine concentration ranged from 1·53 μmol/l on day 3 to 1·84 μmol/l on day 28 (linear effect P=0·07; quadratic effect P>0·05). The results of this study show sow colostrum and milk provide polyamines for sucking piglets before weaning, which could potentially modulate intestinal maturation.