Mothers of preterm infants are at risk for poor sleep quality, which may adversely affect their health, maternal-infant attachment, and infant caretaking activities. This study examined the relationship of an 8-week relaxation guided imagery intervention on sleep quality and the association between sleep quality and maternal distress (perceived stress, depressive symptoms, and state anxiety) in 20 mothers of hospitalized preterm infants. Mothers received a CD (compact disc) with three 20-minutes recordings and were asked to listen to at least 1 recording daily for 8 weeks. This analysis used self-report data gathered at baseline and 8 weeks. Pearson correlations were used to examine the relationships between mean cumulative relaxation guided imagery use and measures of maternal distress and sleep quality scores at 8 weeks. Complete data on 19 mothers were available for analysis. At 8 weeks, higher mean relaxation guided imagery use was inversely correlated with sleep quality scores (r = −0.30); sleep quality scores were positively correlated with stress (r = 0.42), depressive symptoms (r = 0.34), and anxiety (r = 0.39) scores. In mothers of preterm infants, sleep quality was negatively affected by mental distress and may be improved by a guided imagery intervention.