The problem in exclusive breastfeeding was the low understanding of mothers, families and communities about breastfeeding. The habit of giving food/drink early from some people also triggers the lack of success of exclusive breastfeeding. This study aimed to determine the relationship between mother's level of knowledge about exclusive breastfeeding and mother's motivation in exclusive breastfeeding. This research design used correlation analytic with cross sectional approach. The population in this study was all mothers who had children aged > 6-12 months in Randukisi Hamlet, Cukurgondang Village, Grati District, Pasuruan Regency, as many as 39 people. The sampling technique of this research was purposive sampling. The samples in this study were 27 people. The research instrument used a questionnaire. Data analysis used Spearman Rho test. The results suggested that most respondents had good knowledge about exclusive breastfeeding, as many as 16 respondents (59.3%) and most respondents had high motivation in exclusive breastfeeding, as many as 19 respondents (70.4%). The results of the Spearman Rho test suggested that p-value = 0.000 or less than (0.05) so that H1 was accepted, meaning that there was relationship between the level of knowledge about exclusive breastfeeding and motivation in exclusive breastfeeding to mothers in Grati District, Pasuruan Regency. Breastfeeding mothers were expected to give exclusive breastfeeding to infants aged 0-6 months and seeked as much information as possible through mass media such as the internet, or asked health workers a lot about exclusive breastfeeding to dispel myths and wrong assumptions about exclusive breastfeeding