The aim of this study was to examine the psychometric properties of the 11-item Breast Milk Expression Experience Scale and determine the level of breast milk expression experience of mothers after preterm delivery in Turkey. 165 mothers who agreed to participate between February 2019 and March 2020 used the Breast Milk Expression Experience Scale (BMEE-S). The general Cronbach alpha coefficient was 0.82 for the BMEE-S. The fit indices calculated by confirmatory factor analysis were χ (41) = 87.95, p = .00003, χ2/sd = 2.15, GFI = 0.91, NNFI = 0.93, CFI = 0.95, RMSEA = 0.08 and SRMR = 0.078. The BMEE-S three-factor structure was verified by the confirmatory factor analysis. The BMEE-S was a valid and reliable instrument for mothers of preterm infants. Multiparity and high-risk pregnancy history negatively affected the milk expression experience, whereas spousal support positively affected it.Impact statementWhat is already known on this subject? The risk of infectious diseases, obesity, diabetes, and impaired intellectual development increases in children who do not breast milk (Verduci et al. 2014). International breastfeeding guidelines recommend supporting all mothers to start breastfeeding within one hour of birth, and counselling mothers who are separated from their babies about expressing milk.What the results of this study add? The breast milk expression experience scale is a valid and reliable tool for women who give preterm birth and express milk. The experience of expressing breast milk can affect the amount of milk that passes from mother to baby. Multiparity and high risk pregnancy history of mothers negatively affects the milk expression experience while husband support positively affects the milk expression experience.What the implications are of these findings for clinical practice and/or further research? Our study provides a quantitative examination of the experiences of mothers who are separated from their babies. The BMEE-S should be adapted to different cultures and the experiences of mothers in this process should be determined.