This study has analyzed the case of success and failure of Yello Mobile, which grew through the stock exchange M&A. This study examined the benefits of stock exchange method which was the key behind the rapid growth of Yello Mobile and explained why ventures aim to create synergy through network formation in the mobile service industry. Yello Mobile grew up to be the second Unicorn in Korea and was successful in the early period while the analysis on financial statements of Yello Mobile showed that its financial performance has been a failure since 2017. Some of Yello Mobile’s subsidiary companies in the advertising and healthcare sectors have been successfully listed at the KOSDAQ market. The reasons for the failure of Yello Mobile may be summarized in the three ways. First, the management capability and internal control of Yello Mobile were weak. Second, there was no effective synergy due to conflicting interests among founders. Third, focusing only on growth strategies through M&A, it failed to pursue fundamental corporate value. On the other hand, Future Stream Networks and Carelabs are the two successful cases of IPO and operating in advertising and healthcare sectors. The case of Yello Mobile, which experienced the rapid success and failure in 2010’s, provides useful implications for the founders and managers of start-ups to prevent the failure and continue to grow.