Yogurt is a fermented product made from animal milk, using certain starter bacteria such as Lactobacillus bulgaricus and Streptococcus thermophilus. This study focuses on making yogurt from blondo which is added with mature coconut water and combined with cornstarch as a stabilizing agent. The treatments in this study were a comparison of coconut water with regular water at proportions of 0%, 50%, and 100%, as well as the addition of cornstarch at 0%, 2%, and 4%. This study is experimental in nature with an experimental design using a factorial Randomized Block Design (RBD). Data analysis was conducted using an ANOVA test at a significance level of α=0.05. The analysis results each showed a pH value between 4.21 and 4.32, free fatty acids (FFA) ranging from 1.09% to 1.26%, lactic acid 0,45% to 0,53%, total lactic acid bacteria (LAB) reaching 2.9 x 10^6 CFU/ml, viscosity between 0.013 g.cm/sec to 0.42 g.cm/sec (poise). Yogurt separation on the first day ranges from 0% to 75%, while on the fifth day it ranges from 0% to 77%. Organoleptic tests for taste showed a liking score between 2.3 (dislike slightly) to 5 (like), aroma liking score between 2.7 (dislike slightly) to 4 (like slightly), and color liking score between 2.5 (dislike slightly) and 5 (like).