This research was conducted at PT. Pustaka Benua Medan Continental Library. In this study testing and analyzing the influence of brand credibility on customer loyalty was done at PT. Pustaka Benua Medan. Decreasing customer loyalty is caused by brand reliability. The theory used in this study relates to the theory of service quality and customer satisfaction. In this study, the method used by the author is quantitative analysis method. The types of data used in this study are primary data and secondary data.This study uses the random sampling method by taking a number of populations a as sample to be tested using SPSS. The scale used to measure the variable is Likert scale. The sample population is 36 respondents. In this study, the researcher used a saturated sampling technique. Saturated sampling is a sampling technique if all members of the population are used as samples. Thus the numbers of samples used in this study were 36 respondents Based on the results of testing there is influence of brand credibility on customer loyalty at PT. Pustaka Benua Medan. The Determination Coefficient Test results obtained is the R square value of 0.416, this means 41.6% of the dependent variable is customer loyalty (Y) which can be explained by the independent variable brand credibility (X) while the remaining 58.4% is explained by other variables not used in this research.