Maintaining stable physiological responses may be important for the growth and development of preterm infants. The purpose of our study was to evaluate the effects of olfactory stimulation with maternal breast milk on the occurrence of abnormal physiological responses in preterm infants. With a non-equivalent control group pretest-posttest design, 13 preterm infants in the experimental group and 18 preterm infants in the control group completed the intervention. The intervention was implemented three times a day for 5 days in a row with 2 hours of administration per intervention. The frequency of abnormal physiological responses was assessed over 6 days (one day before intervention administration and 5 days during intervention administration). With repeated-measures analysis of variance, the experimental group showed a significantly lower frequency of apnea than the control group ( p = .021). Olfactory stimulation with maternal breast milk may be an effective nursing intervention for reducing apnea episodes in preterm infants.