Service quality and customer satisfaction are the keys for the companies to compete and grow. Based on interview and finding there are several problems, the employee is not responsive and also the waiter is lack of initiative regarding the tableware that needed to be changed. Therefore, the writer decided to analyze service quality to achieved customer satisfaction at Grand Maximum Seafood Restaurant Medan.Service quality is related to customer satisfaction. If the quality of service provided by the company that can meet customer expectations, the customer will be satisfied and that is what is called customer satisfaction.This research is a quantitative research using survey research. The sampling technique used is convenient sampling, which is done by choosing the sample as freely by the writer, which is 67 customers. Data analysis in this study are descriptive statistics, validity test, reliability test, normality test, correlation test, determination test, simple linear regression test, and z test.This research was conducted at Grand Maximum Seafood Restaurant Medan. Based on the results of data analysis, service quality has a relationship with customer satisfaction.The z test results show that Zcount> Ztable (5.889 > 1.96) which means that service quality has an effect towards customer satisfaction at Grand Maximum Seafood Restaurant Medan. Based on this study, the writer hope this research can be used as a reference to improve service quality at the restaurant and recommend to restaurants to do roleplay training to employees regularly in order to improve and maintain service quality to achieve customer satisfaction.