Purpose: To determine the sleep quality and fatigue levels of mothers in the period of transition additional food. Materials and methods: It was a relation seeking descriptive study which contained 377 mothers who had sixth month babies. The datas of the study was collected in Samsun between June and December 2015 with "Personal Information Form", "Pittsburgh Sleep Quality Questionnaire” and "Piper Fatigue Scale”. The statistical analysis of the data was made with using percentages, means, t test, ANOVA, Kruskal Wallis, Man Whitney U and correlation test. Results: It was found that the average age of mothers was 28.1±5.2 years, 44.8% of them high school graduated, 25.2% of them working outside, 78.8% of them lived in a nuclear family. It was determined 69.6% of the babies passed the additional food before sixth month, and 31.5% of them passed with baby formula. It was appointed that the 65.3% of mothers in period of transition additional food experienced sleep problems and 66.6% of them experienced fatigue. It was found a positive weak and significant correlation between the mothers Pittsburgh Sleep Quality Questionnaire scores and and Piper Fatigue Scale scores (p<0.05). Conclusion: It was seen that in the period of transition additional food, the mothers experience problems about the passing time, first foods and feeding method and this situation causes insomnia and fatigue. According to the results it could be recommended to development of training programs for the improvement of mothers' sleep quality and fatigue levels.