Postpartum period or puerperium starts after reproductive organs have returned to normal and completed after approximately 42 days. Health workers must provide adequate breastfeeding information along with how to breastfeed as long as pandemic era, in determining the effectiveness of “Pintar ASI” application on knowledge level of postpartum women as the medium for delivering information about how to breastfeed. The research employs a quasi experimental study, pre-test and post-test intervention. Samples of 50 people are taken with purposive sampling technique, 25 people on experiment group and 25 from control group. The research instrument used google form which contains of questionnaire regarding knowledge about breastfeeding and “Pintar ASI” application that is already available on google site. The application is used for 7 days. Data analysis are used to determine the difference of knowledge score prior and after the usage of “Pintar ASI” application using test of paired sample t-test, p-value = 0.000 is obtained and because the data are homogeneous, the independent sample t-test is carried to determine the difference between the two groups, with knowledge result obtained of p value = 0.000. The result demonstrates that there is a significant difference between knowledge level of postpartum women prior and giving “Pintar ASI” application in the working area of Medan johor with the result obtained of p value = 0.000. The result demonstrates that there is a significant difference between knowledge level of postpartum women prior and giving “Pintar ASI” application.